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7 May 2013

Volume 113, Issue 17, Articles (17xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 113, 174302 (2013); http://dx.doi.org/10.1063/1.4798262 (4 pages)

Yuichiro Kurokawa, Takehiko Hihara, and Ikuo Ichinose
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back to top Magneto-Optic, Magnetoelastic, and Magnetocaloric Materials

Effect of buffer layer and external stress on magnetic properties of flexible FeGa films

Xiaoshan Zhang, Qingfeng Zhan, Guohong Dai, Yiwei Liu, Zhenghu Zuo, Huali Yang, Bin Chen, and Run-Wei Li

J. Appl. Phys. 113, 17A901 (2013); http://dx.doi.org/10.1063/1.4793602 (3 pages)

Online Publication Date: 27 February 2013

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We systematically investigated the effect of a Ta buffer layer and external stress on the magnetic properties of magnetostrictive Fe81Ga19 films deposited on flexible polyethylene terephthalate (PET) substrates. The Ta buffer layers could effectively smoothen the rough surface of PET. As a result, the FeGa films grown on Ta buffer layers exhibit a weaker uniaxial magnetic anisotropy and lower coercivity, as compared to those films directly grown on PET substrates. By inward and outward bending the FeGa/Ta/PET samples, external in-plane compressive and tensile stresses were applied to the magnetic films. Due to the inverse magnetostrictive effect of FeGa, both the coercivity and squareness of hysteresis loops for FeGa/Ta films could be well tuned under various strains.
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75.70.Ak Magnetic properties of monolayers and thin films
68.60.Bs Mechanical and acoustical properties
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
81.40.Lm Deformation, plasticity, and creep

The universal behavior of inverse magnetocaloric effect in antiferromagnetic materials

Anis Biswas, Sayan Chandra, Tapas Samanta, M. H. Phan, I. Das, and H. Srikanth

J. Appl. Phys. 113, 17A902 (2013); http://dx.doi.org/10.1063/1.4793768 (3 pages)

Online Publication Date: 28 February 2013

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We report the universal behavior of inverse magnetocaloric effect (IMCE) in antiferromagnetic materials. In contrast to the universal behavior of conventional magnetocaloric effect often observed in ferromagnetic systems, a phenomenological universal master curve can be constructed to describe the temperature dependence of magnetic entropy change for IMCE without rescaling the temperature axis. The proposed universal curve method allows extrapolating the magnetic entropy change of an IMCE material, which would be imperative to judge its suitability in actual magnetic refrigeration devices.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Ee Antiferromagnetics
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Positive and negative magnetocaloric effects in CeSi

J. L. Snyman, E. Carleschi, B. P. Doyle, and A. M. Strydom

J. Appl. Phys. 113, 17A903 (2013); http://dx.doi.org/10.1063/1.4793779 (3 pages)

Online Publication Date: 28 February 2013

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We present a study of the magnetocaloric effect (MCE) in the commensurate antiferromagnet CeSi. We show that the MCE exhibits both positive and negative components, the former indicative of a magnetic configurational entropy increases upon isothermal magnetisation. We describe the Hamiltonian ℋ of the system as a simple model antiferromagnetic Hamiltonian where spins are ferromagnetically aligned in the ac-plane, while planes are weakly antiferromagnetically coupled along the b-axis (consistent with μSR experimental results). We show that ℋ reproduces both the positive and the negative MCE for applied fields up to 30 kOe, while in larger fields the magnitude of the negative component (indicative of an overall suppression of magnetic configurational entropy) is larger than expected from our model.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
65.40.gd Entropy
75.10.Dg Crystal-field theory and spin Hamiltonians

Crystal structure, magnetic properties, and the magnetocaloric effect of Gd5Rh4 and GdRh

C. L. Wang, J. D. Zou, J. Liu, Y. Mudryk, K. A. Gschneidner, Jr., Y. Long, V. Smetana, G. J. Miller, and V. K. Pecharsky

J. Appl. Phys. 113, 17A904 (2013); http://dx.doi.org/10.1063/1.4793775 (3 pages)

Online Publication Date: 4 March 2013

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The crystal structures of Gd5Rh4 and GdRh have been studied by powder and single crystal x-ray diffraction. The results show that Gd5Rh4 is isotypic with Pu5Rh4 and the bond length of the short Rh-Rh dimer is 2.943(4) Å. According to heat capacity measurements in zero magnetic field, the magnetic ordering temperature of Gd5Rh4 is 13 K, in agreement with magnetization measurements. Both the heat capacity peak shape and the positive slope of the Arrott plots at Curie temperature (TC) indicate the second-order nature of the magnetic transition. The temperature dependence of magnetization of Gd5Rh4 measured in 1 kOe applied field indicates noncollinear magnetic ordering that may change into nearly collinear ferromagnetic ordering by increasing the magnetic field. GdRh is ferromagnetic below TC = 22 K. Moderate magnetocaloric effects and relatively high refrigerant capacities are observed in Gd5Rh4 and GdRh.
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61.66.Dk Alloys
65.40.Ba Heat capacity
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Cc Other ferromagnetic metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

The effect of magnetic annealing on the magnetostriction for Sm-Dy-Fe rod alloys

Bowen Wang, Zhihua Wang, Ling Weng, Wenmei Huang, Ying Sun, and Baozhi Cui

J. Appl. Phys. 113, 17A905 (2013); http://dx.doi.org/10.1063/1.4794282 (3 pages)

Online Publication Date: 5 March 2013

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The Sm0.86Dy0.14Fex (x = 1.85−2.05) magnetostrictive alloys have been prepared with arc-melting and then cast into a copper mold with a diameter of 8 mm. It is found that the magnetostriction (λ// − λ⊥) increases from −900 × 10−6 for untreated rod alloys to −1200 × 10−6 for magnetically annealed rod alloys at the magnetic field of 640 kA/m. In the magnetic annealing temperature range of 483−643 K, the magnetostriction value exhibits a peak at 543 K. The variation of magnetostriction and magnetization with magnetic fields has been determined and the mechanism of domains' movements has been discussed. This result is very important to improve the magnetostrictive property of Sm-Dy-Fe rod alloys.
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75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.80.+q Magnetomechanical effects, magnetostriction
81.10.Fq Growth from melts; zone melting and refining
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Normal and inverse magnetocaloric effects in ferromagnetic Pr0.58Sr0.42MnO3

D. V. Maheswar Repaka, M. Aparnadevi, Pawan Kumar, T. S. Tripathi, and R. Mahendiran

J. Appl. Phys. 113, 17A906 (2013); http://dx.doi.org/10.1063/1.4793599 (3 pages)

Online Publication Date: 6 March 2013

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We report magnetization, magnetic entropy change (ΔSm), and its correlation with magnetoresistance (MR) in Pr0.58Sr0.42MnO3. It is shown that the magnetization upon field-cooling shows a steplike decrease at TS = 134 K much below the ferromagnetic transition (TC = 300 K). While the low temperature transition is first-order, the high temperature transition is second-order as suggested by the hysteresis behavior in magnetization. In a magnetic field range accessible with an electromagnet, the magnetic entropy decreases at TC (ΔSm = −2.33 J/kg K with a refrigeration capacity of 65.88 J/kg for a magnetic field change of ΔH = 2 T) whereas it increases at TS (ΔSm = +0.7 J/kg K) upon magnetization. The unusual inverse magnetocaloric effect found at TS within ferromagnetic state is ascribed to orthorhombic to monoclinic structural transition. We show that ΔSm versus T curves under different magnetic fields can be collapsed into a single master curve using a scaling method. Importantly, we find that negative MR increases linearly with −ΔSm in the paramagnetic state at all magnetic fields above TC and at higher magnetic fields below TC. Such a close correlation between the magnetoresistance and the magnetic entropy change can be exploited to design efficient magnetocaloric materials.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.70.K- Solid-solid transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Effect of crystallographic alignment on the magnetocaloric effect in alloys near the Ni2MnGa stoichiometry

Anit K. Giri, Brigitte A. Paterson, Michael V. McLeod, Cindi L. Dennis, Bhaskar S. Majumdar, Kyu C. Cho, and Robert D. Shull

J. Appl. Phys. 113, 17A907 (2013); http://dx.doi.org/10.1063/1.4793608 (3 pages)

Online Publication Date: 6 March 2013

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Prior to the development of commercial applications of magnetic refrigerator technology, a large magnetocaloric effect (MCE) in polycrystalline materials must be realized for relatively low magnetic field changes. To increase the MCE, a crystallographic alignment technique, consisting of thermal cycling about the martensite phase transition temperature under a compressive stress, was applied to Heusler alloys with nominal composition Ni2+xMn1−xGa (x = 0.14, 0.16). Magnetic measurements prior to grain alignment show that the maximum entropy changes of −16 J kg−1K−1 and −24 J kg−1K−1 for samples with x = 0.14 and 0.16, respectively, occurred for a magnetic field change of 7 T. After grain alignment, there was a 56%–79% enhancement of the maximum magnetic entropy change for the same magnetic field change of 7 T. This suggests that thermal cycling under compressive stress may either increase grain alignment (e.g., texture) along the magnetic easy (001) axis, and/or enhance the ease with which a magnetic field is later able to grow favorably oriented twin variants that manifests as an increase of magnetization of the material. Therefore, such an alignment technique may be utilized to enhance the MCE of similar Heusler alloys.
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75.30.Sg Magnetocaloric effect, magnetic cooling
61.66.Bi Elemental solids
61.66.Dk Alloys
64.70.kd Metals and alloys
81.40.Lm Deformation, plasticity, and creep
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Kf Martensitic transformations

Age splitting of the La(Fe1−xSix)13Hy first order magnetocaloric transition and its thermal restoration

Carl B. Zimm and Steven A. Jacobs

J. Appl. Phys. 113, 17A908 (2013); http://dx.doi.org/10.1063/1.4794976 (3 pages)

Online Publication Date: 8 March 2013

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The La(Fe1−xSix)13Hy system has a first order ferromagnetic phase transition with a large magnetocaloric effect for 0.11 < x < 0.13. Such materials produced the highest currently published cooling power of a magnetic refrigerator. Adjusting the H content, y allows selection of any Curie point Tc from ∼200 K to 330 K, but hydrogen-unsaturated material (y < 1.6) with a first order transition exhibits an unusual instability. If La(Fe1−xSix)13Hy is held within a few K of its initial Tc, an initially single magnetic transition, with a sharp differential scanning calorimetry peak, gradually splits into two transitions separated by a large temperature interval. The ultimate splitting interval depends almost linearly on (1.6-y) and Tc. If the material is held more than 10 K above or below Tc, an initially sharp transition is retained, and a split transition is restored to its original sharp single transition. The recovery rate increases with temperature. For temperatures above 320 K, the recovery rate is rapid enough to allow overnight recovery of magnetocaloric material that is in a split state. This method was employed to maintain high performance of La(Fe1−xSix)13Hy in a magnetic refrigerator. In order to verify that the recovery process involves the macroscopic movement of hydrogen within the solid, a portion of 0.2 mm diameter particle material with a split transition was ground into particles of 0.05 mm diameter. The unground 0.2 mm particles and the ground 0.05 mm particles were held at 13 K above Tc. The 0.3 mm particles recovered their initial single transition, but the 0.05 mm particles, when examined as a group, retained their split line, presumably because they had been separated into particles with differing total hydrogen fraction y.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Texture development in Galfenol wire

A. J. Boesenberg, J. B. Restorff, M. Wun-Fogle, H. Sailsbury, and E. Summers

J. Appl. Phys. 113, 17A909 (2013); http://dx.doi.org/10.1063/1.4794186 (3 pages)

Online Publication Date: 11 March 2013

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Galfenol (Fe-Ga alloy) wire fabrication provides a low cost alternative to directional solidification methods. This work evaluates the compositional dependence of the wire drawing suitability of Fe-Ga and characterizes the microstructural and magnetic properties of these wires. Wire has been produced with Ga contents between 10 at. % and 17 at. % to allow determination of the ductile to brittle transition (DTBT) in wire manufacture. Published results on chill cast bend specimens indicated that a DTBT occurs at roughly 15 at. % Ga. This DTBT was observed under tensile loading with a corresponding change in fracture behavior from transverse fracture to intergranular fracture. For improved magnetostrictive performance, higher Ga contents are desired, closer to the 17 at. % Ga evaluated in this work. Electron backscattered diffraction B-H loop and resonance measurements as a function of magnetic field (to determine modulus and coupling factor) are presented for as-drawn, furnace, and direct current (DC) annealed wire. Galfenol wire produced via traditional drawing methods is found to have a strong 〈110〉 (α) texture parallel to the drawing direction. As-drawn wire was observed to have a lower magnetic permeability and larger hysteresis than DC annealed wire. This is attributed to the presence of a large volume of crystalline defects; such as vacancies and dislocations.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mj Brittleness
62.20.mm Fracture
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.10.Fq Growth from melts; zone melting and refining

A hybrid-exchange density functional study of Ca-doped LaMnO3

R. Korotana, G. Mallia, Z. Gercsi, and N. M. Harrison

J. Appl. Phys. 113, 17A910 (2013); http://dx.doi.org/10.1063/1.4794877 (3 pages)

Online Publication Date: 13 March 2013

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In this work, hybrid-exchange density functional theory calculations are carried out to determine the effects of A-site doping on the electronic and magnetic properties of the manganite series La1−xCaxMnO3. This study focuses on the nature of the ground state for an ordered Ca distribution. We show that the hybrid exchange functional, B3LYP, provides an accurate and consistent description of the electronic structure for LaMnO3 and La0.75Ca0.25MnO3. The magnetic ground states for the compositions studied are predicted correctly and comparisons have been made to available experimental data. This provides a basis for a first principles description of the magnetocaloric effect in La1−xCaxMnO3.
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75.30.Et Exchange and superexchange interactions
75.30.Sg Magnetocaloric effect, magnetic cooling
71.20.Ps Other inorganic compounds
71.70.Gm Exchange interactions

Influence of particle size on the hydrogenation in La(Fe, Si)13 compounds

H. Zhang, Y. Long, E. Niu, X. P. Shao, J. Shen, F. X. Hu, J. R. Sun, and B. G. Shen

J. Appl. Phys. 113, 17A911 (2013); http://dx.doi.org/10.1063/1.4794975 (3 pages)

Online Publication Date: 13 March 2013

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The influence of particle size on the hydrogenation of La(Fe, Si)13 compounds is studied in detail. The average TC increases largely from 240 K to 308.5 K due to the enhancement of surface area by reducing the particle size. Besides, it is found that small particle size and narrow size range would improve the homogeneity of hydrogen distribution. The magnetic entropy change (ΔSM) decreases slightly after hydrogenation, but the maximum value of −ΔSM of small LaFe11.7Si1.3C0.2Hx still remains a relatively large value of 14.4 J/kg K for a low magnetic field change of 2 T. It is also noted that the hydrogen-saturated LaFe11.7Si1.3C0.2H1.7 exhibits a great stability under a high pressure of 1.36 GPa, and this result is favorable to the further processing and applications of La(Fe, Si)13 compounds.
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82.30.-b Specific chemical reactions; reaction mechanisms
75.30.Sg Magnetocaloric effect, magnetic cooling
62.50.-p High-pressure effects in solids and liquids
65.40.gd Entropy

Magnetic entropy change and refrigerant capacity of rapidly solidified TbNi2 alloy ribbons

J. L. Sánchez Llamazares, C. F. Sánchez-Valdes, P. J. Ibarra-Gaytan, Pablo Álvarez-Alonso, P. Gorria, and J. A. Blanco

J. Appl. Phys. 113, 17A912 (2013); http://dx.doi.org/10.1063/1.4794988 (3 pages)

Online Publication Date: 13 March 2013

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The magnetocaloric effect in TbNi2 alloy ribbons synthesized by rapid solidification was investigated. This material crystallizes in a superstructure of the cubic Laves phase structure type C15 (space group F-43m). The saturation magnetization and Curie temperature are MS = 134 ± 2 A m2 kg−1 and TC = 37 ± 1 K, respectively. For a magnetic field change of 5 T, the material shows a maximum magnetic entropy change |ΔSMpeak| = 13.9 J kg−1 K−1, with a full-width at half-maximum δTFWHM = 32 K, and a refrigerant capacity RC = 441 J kg−1. The RC value is similar to those reported for other magnetic refrigerants operating within the temperature range of 10-80 K. Finally, it is worth noting that the use of rapid solidification circumvents the necessity for long-term high-temperature homogenization processes normally needed with these RNi2 alloys.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Fb Solidification
61.66.Dk Alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Microstructure, martensitic transitions, magnetocaloric, and exchange bias properties in Fe-doped Ni-Mn-Sn melt-spun ribbons

X. G. Zhao, M. Tong, C. W. Shih, B. Li, W. C. Chang, W. Liu, and Z. D. Zhang

J. Appl. Phys. 113, 17A913 (2013); http://dx.doi.org/10.1063/1.4794881 (3 pages)

Online Publication Date: 14 March 2013

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The effects of Fe substitution for Ni on microstructure, phase transformations, magnetocaloric effect, and exchange-bias behavior of the Ni46−xFexMn43Sn11 (x = 0–3) alloy ribbons have been investigated. The free surface of as-spun Fe-doped ribbons shows the granular microstructure containing multiple shapes (the tree leaf-like, small columnar grain, etc.), while the ordered columnar grains are observed in fracture cross-section. The martensitic structural transition temperature (TM) of as-annealed ribbons decreases from 240 K for x = 0 to 185 K for x = 3 due to the decrease in valence electron concentration, while the Curie temperature of the austenitic phase remains almost unchanged (TC = 275 K). The positive values of magnetic entropy changes (+ΔSM), around TM, are 21.0, 29.1, 24.1, and 14.8 J/kg K for x = 0–3, respectively, while the negative −ΔSM values vary in 3.0–3.5 J/kg K range around TC, under a field change of 0–5 T. The values of exchange-bias field (HE) at 10 K change in the range of 469 to 534 Oe and the coercivity (HC) slightly decreases from 245 to 186 Oe, respectively, as x is increased.
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75.30.Sg Magnetocaloric effect, magnetic cooling
81.30.Kf Martensitic transformations
81.40.Gh Other heat and thermomechanical treatments
64.70.kd Metals and alloys
65.40.gd Entropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Large refractive index in BiFeO3-BiCoO3 epitaxial films

Hiromi Shima, Ken Nishida, Takashi Yamamoto, Toshiyasu Tadokoro, Koichi Tsutsumi, Michio Suzuki, and Hiroshi Naganuma

J. Appl. Phys. 113, 17A914 (2013); http://dx.doi.org/10.1063/1.4794878 (3 pages)

Online Publication Date: 18 March 2013

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Rhombohedral (R-) and tetragonal (T-) Bi(Fe,Co)O3 (BFCO) films were epitaxially grown on the SrTiO3 (100) substrates, and the optical properties of the BFCO films were evaluated by spectroscopic ellipsometry. It was revealed that the refractive indexes of R- and T-BFCO epitaxial films were 2.93 and 2.86 at wavelength of 600 nm, and 2.65 and 2.59 at 1550 nm, respectively, which are comparable to the pure BiFeO3. The refractive index of the R-BFCO film was totally larger than that of the T-BFCO film; it might be caused by structural strain and local symmetry breaking. It was confirmed that the extinction coefficients of both films were almost zero at wavelengths larger than 600 nm. In addition, the optical band gaps of the R- and T-BFCO films were estimated to be 2.78 and 2.75 eV, respectively. It can expect that the BFCO film has a possibility to use optical-magnetic field sensor working at room temperature.
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78.66.Nk Insulators
81.15.Cd Deposition by sputtering
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

Magnetization model for a Heusler alloy

Virgil Provenzano, Edward Della Torre, and Lawrence H. Bennett

J. Appl. Phys. 113, 17A915 (2013); http://dx.doi.org/10.1063/1.4795212 (3 pages)

Online Publication Date: 18 March 2013

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Close to room temperature, the off-stoichiometric Ni50Mn35In15 Heusler alloy is known to undergo a first-order magnetostructural transition. This paper presents a new model that closely mimics the magnetic behavior of the virgin curve and that of the M-H loops within the temperature range where the alloy undergoes the first-order transition. The virgin curve and the M-H loops relevant to the model were measured at 280 K. Since our data show that 280 K is above the start of the transition, it implies that at this temperature the alloy is in a mixed state. The mixed state refers the presence of two distinct magnetic states. The model and mechanism we propose to explain the complex magnetic behavior of the virgin curve and of the M-H loops pertain to the action of the applied field on the transition between the two magnetic states. Both the model and the proposed mechanism provide new insight about the complex magnetic behavior displayed by the Ni50Mn35In15 alloy within the first-order transition.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.kd Metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Low hysteresis and large room temperature magnetocaloric effect of Gd5Si2.05−xGe1.95−xNi2x (2x = 0.08, 0.1) alloys

X. C. Zhong, J. X. Min, Z. W. Liu, Z. G. Zheng, D. C. Zeng, V. Franco, and R. V. Ramanujan

J. Appl. Phys. 113, 17A916 (2013); http://dx.doi.org/10.1063/1.4795434 (3 pages)

Online Publication Date: 18 March 2013

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Gd5Si2.05−xGe1.95−xNi2x (2x = 0.08, 0.1) alloys were prepared by arc melting followed by annealing at 1273 K for 96 h. Mixed monoclinic Gd5Si2Ge2-type phase, orthorhombic Gd5Si4-type phase, and a small amount of Gd5Si3-type phase were obtained in these alloys. Gd5Si2.01Ge1.91Ni0.08 alloy undergoes a second-order transition (TC) around 300 K, whereas Gd5Si2Ge1.9Ni0.1 alloy exhibits two transitions including a first-order transition (TCІІ) at ∼295 K and second-order transition (TCІ) at ∼301 K. Ni substitution can effectively reduce the thermal hysteresis and magnetic hysteresis while maintaining large magnetic entropy change. The maximum magnetic entropy changes (|ΔSMmax|) of Gd5Si2.05−xGe1.95−xNi2x alloys with 2x = 0.08 and 0.1 are 4.4 and 5.0 J kg−1 K−1, respectively, for 0–2 T, and are 8.0 and 9.1 J kg−1 K−1, respectively, for 0–5 T. Low hysteresis performance and relatively large magnetic entropy change make these alloys favorable for magnetic refrigeration applications.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Relationships between magnetization and dynamic stress for Galfenol rod alloy and its application in force sensor

Ling Weng, Bowen Wang, M. J. Dapino, Ying Sun, Li Wang, and Baozhi Cui

J. Appl. Phys. 113, 17A917 (2013); http://dx.doi.org/10.1063/1.4795328 (3 pages)

Online Publication Date: 19 March 2013

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Magnetization versus dynamic stress of Fe81.6Ga18.4 is measured at 4.0 kA/m bias magnetic field and −7.0 MPa compressive pre-stress. The magnetization and stress curves show that magnetization decreases with increasing compressive stress. Magnetization increases with increasing stress frequency at −20 MPa compounded stress. The output voltage from the pickup coil of a Galfenol force sensor is measured when the frequency and amplitude of dynamic force vary. The measurements show that the output voltage increases proportionally with increasing force frequency and amplitude. When the bias magnetic field is 4.0 kA/m, a maximum output voltage of 57 mV is measured at −7.0 MPa compressive pre-stress.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Tuning the Curie temperature in γ-FeNi nanoparticles for magnetocaloric applications by controlling the oxidation kinetics

Huseyin Ucar, John J. Ipus, D. E. Laughlin, and M. E. McHenry

J. Appl. Phys. 113, 17A918 (2013); http://dx.doi.org/10.1063/1.4795012 (3 pages)

Online Publication Date: 20 March 2013

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See Also: Publisher's Note

Show Abstract
Mechanically alloyed Fe70Ni30 and Fe72Ni28 alloys were characterized in terms of their structural and magnetic properties. Previous studies showed that single phase FCC γ-FeNi alloys with ∼26-30 at. % Ni have Curie temperatures, Tc, near room temperature. Having Tc near room temperatures along with large magnetization makes γ-FeNi alloys attractive for room temperature magnetocaloric cooling technologies. To obtain a single γ-phase, particles were solution annealed in the γ-phase field and water quenched. The preferential oxidation of Fe during ball milling was used as a means to tune the Curie temperature, Tc, of the alloy. Refrigeration capacities, RCFWHM, of the Fe70Ni30 and the Fe72Ni28 alloys were calculated to be ≈470 J/kg and 250 J/kg at 5 T, with peak temperatures ≈363 K and ≈333 K, respectively. The RCFWHM for the Fe70Ni30 is higher than the previously reported Nanoperm (Fe70Ni30)89Zr7B4 type alloy and on the same order of magnitude with other Fe-based alloys. The maximum magnetic entropy change values observed for the Fe70Ni30 and the Fe72Ni28 are 0.65 and 0.5 J kg−1 K−1, respectively, at a field of 5 T. These are smaller than those of rare earth magnetic refrigerants showing first order transformation behavior. The larger RCFWHM value results mainly from the width of the magnetic entropy curve in these types of materials. We discuss the economic advantage of these rare earth free refrigerants.
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75.75.Cd Fabrication of magnetic nanostructures
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Two-dimensional magnetic property measurement for magneto-rheological elastomer

Jianbin Zeng, Youguang Guo, Yancheng Li, Jianguo Zhu, and Jianchun Li

J. Appl. Phys. 113, 17A919 (2013); http://dx.doi.org/10.1063/1.4796046 (3 pages)

Online Publication Date: 22 March 2013

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Magneto-rheological elastomer (MRE) is a new kind of smart material. Its rheological properties can be altered and controlled in a real time manner when it is applied an external magnetic field. For calculating magnetic properties of MRE material, usually Maxwell-Garnet equation is used to acquire an approximately effective permeability. This equation treats the magnetic property of particles as linear. However, when the applied magnetic field is alternating or rotating, the nonlinearity of magnetic property and magnetic hysteresis cannot be neglected. Hence, the measurement and modelling of the magnetic properties under alternating and rotating magnetic fields are essential to explore new applications of the material. This paper presents the investigation on the magnetic hysteresis properties of MRE material under one-dimensional (1-D) alternating and two-dimensional (2-D) rotating magnetic field excitations. A kind of MRE material, consisting of 70% carbonyl iron particles, 10% silicone oil, and 20% silicone rubber, was used to investigate the magnetic properties. The diameter of carbonyl iron particles is 3–5 μm. The measurement results, such as the relations between magnetic field intensity (H) and magnetic flux density (B) under different magnetic field excitations on the MRE sample, have been obtained and analyzed. These data would be useful for design and analysis of MRE smart structures like MR dampers.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
83.60.Np Effects of electric and magnetic fields
83.80.Gv Electro- and magnetorheological fluids
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Mm Magnetic liquids
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Field dependent magnetic anisotropy of Fe1−xZnx thin films

Damon A. Resnick, A. McClure, C. M. Kuster, P. Rugheimer, and Y. U. Idzerda

J. Appl. Phys. 113, 17A920 (2013); http://dx.doi.org/10.1063/1.4796048 (3 pages)

Online Publication Date: 22 March 2013

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Using longitudinal magneto-optical Kerr effect in combination with a variable strength rotating magnetic field, called the Rotational Magneto-Optic Kerr Effect (ROTMOKE) method, we show that the magnetic anisotropy for thin Fe82Zn18 single crystal films, grown on MgO(001) substrates, depends linearly on the strength of the applied magnetic field at low fields but is constant (saturates) at fields greater than 350 Oe. The torque moment curves generated using ROTMOKE are well fit with a model that accounts for the uniaxial and cubic anisotropy with the addition of a cubic anisotropy that depends linearly on the applied magnetic field. The field dependent term is evidence of a large effect on the effective magnetic anisotropy in Fe1−xZnx thin films by the magnetostriction.
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75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects
75.70.Ak Magnetic properties of monolayers and thin films
75.80.+q Magnetomechanical effects, magnetostriction

Magnetic properties and magnetocaloric effect of (Mn1−xFex)5Sn3 (x = 0–0.5) compounds

J. H. Xu, X. M. Liu, Y. H. Xia, W. Y. Yang, H. L. Du, J. B. Yang, Y. Zhang, and Y. C. Yang

J. Appl. Phys. 113, 17A921 (2013); http://dx.doi.org/10.1063/1.4798308 (3 pages)

Online Publication Date: 27 March 2013

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The structural and magnetic properties of (Mn1−xFex)5Sn3 compounds have been investigated by x-ray diffraction and magnetic measurements. All the samples crystallize in the hexagonal Ni2In-type structure (P63/mmc) with the lattice parameters and cell volume decreasing almost linearly with the increase of Fe concentration. Besides the spin-glass state transition, the thermomagnetic curves show two other successive magnetic ordering transitions and their temperatures vary with x and show minima when x ∼ 0.2. With increasing Fe content, the difference between the two magnetic ordering temperatures becomes larger gradually from ∼12 K (x = 0) to ∼42 K (x = 0.5) and the magnetization at 5 K increases continuously. The −ΔSM(T) dependence for x = 0.45 exhibits two peaks, leading to a wide temperature range for magnetic refrigeration and thus a considerable magnetic refrigerant capacity (120 J/kg, ΔH = 5 T).
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.10.Dn Growth from solutions
64.70.P- Glass transitions of specific systems
61.66.Dk Alloys
72.15.Jf Thermoelectric and thermomagnetic effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Large magnetocaloric effects over a wide temperature range in MnCo1−xZnxGe

Tapas Samanta, Igor Dubenko, Abdiel Quetz, Shane Stadler, and Naushad Ali

J. Appl. Phys. 113, 17A922 (2013); http://dx.doi.org/10.1063/1.4798339 (3 pages)

Online Publication Date: 27 March 2013

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The magnetic and structural transitions can be controlled to coincide by partial substitution of Zn for Co in MnCo1−xZnxGe, leading to a large magnetocaloric effects over a wide temperature range. The magnetostructural transition from paramagnetic to ferromagnetic state results in magnetic entropy changes (−ΔSM) of 26 J/kg K at 327 K for ΔH = 5 T in the case of x = 0.045. Interestingly, a structurally driven first-order phase transition between two high magnetization states as observed for x = 0.05 and 0.06 also lead to large values of −ΔSM = 31.4 and 20.6 J/kg K for ΔH = 5 T at 281 and 209 K, respectively. The observed large magnetocaloric effects with tunable phase transition temperatures make these materials promising for near room-temperature magnetic cooling applications.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Thermomagnetic analysis of FeCoCrxNi alloys: Magnetic entropy of high-entropy alloys

M. S. Lucas, D. Belyea, C. Bauer, N. Bryant, E. Michel, Z. Turgut, S. O. Leontsev, J. Horwath, S. L. Semiatin, M. E. McHenry, and C. W. Miller

J. Appl. Phys. 113, 17A923 (2013); http://dx.doi.org/10.1063/1.4798340 (3 pages)

Online Publication Date: 27 March 2013

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The equimolar alloy FeCoCrNi, a high-entropy alloy, forms in the face-centered-cubic crystal structure and has a ferromagnetic Curie temperature of 130 K. In this study, we explore the effects of Cr concentration, cold-rolling, and subsequent heat treatments on the magnetic properties of FeCoCrxNi alloys. Cr reductions result in an increase of the Curie temperature, and may be used to tune the TC over a very large temperature range. The magnetic entropy change for a change in applied field of 2T is ΔSm = −0.35 J/(kg K) for cold-rolled FeCoCrNi. Cold-rolling results in a broadening of ΔSm, where subsequent heat treatment at 1073 K sharpens the magnetic entropy curve. In all of the alloys, we find that upon heating (after cold-rolling) there is a re-entrant magnetic moment near 730 K. This feature is much less pronounced in the as-cast samples (without cold-rolling) and in the Cr-rich samples, and is no longer observed after annealing at 1073 K. Possible origins of this behavior are discussed.
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75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Bb Fe and its alloys
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.66.Dk Alloys

Contribution of paramagnetic entropy to magnetocaloric effect in La(FexSi1−x)13

A. Fujita, H. Yako, and M. Kano

J. Appl. Phys. 113, 17A924 (2013); http://dx.doi.org/10.1063/1.4796191 (3 pages)

Online Publication Date: 28 March 2013

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To evaluate paramagnetic fluctuations and their contribution to entropy change of magnetic phase transition, paramagnetic susceptibility of La(Fe0.88Si0.12) was investigated after modifying the magnetic state by application of pressure or by the partial substitution of Ce or Al. Volume reduction by hydrostatic pressure or partial substitution of Ce maintains the value of effective moment peff, and comparison of peff with spontaneous moment at ground state suggests the appearance of disordered local moment in the paramagnetic phase. Reduction of the paramagnetic Curie temperature θp by these modifications is faster than that of the Curie temperature TC. Change in the difference TC −θP is equivalent to that in the entropy change ΔSCC obtained from the Clausius-Clapeyron relation. On the contrary, partial substitution of Al brings about an increase of itinerant character, accompanying a reduction of ΔSCC.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
75.20.En Metals and alloys
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Stress effects on complex permeability spectra of Mn-substituted cobalt ferrite

C. C. H. Lo and B. Fan

J. Appl. Phys. 113, 17A925 (2013); http://dx.doi.org/10.1063/1.4795796 (3 pages)

Online Publication Date: 29 March 2013

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The effects of axial applied stresses on the magnetization processes in Mn-substituted cobalt ferrite (CoMnxFe2-xO4 with x = 0 to 0.4) toroids have been studied by measuring the circumferential complex permeability spectra μ* = μ′ − iμ″ from 1 kHz to 15 MHz. The μ* spectra were described using a dispersion equation to determine the relative susceptibilities due to domain wall motion (χD0) and magnetization rotation (χS0). Mn-substitution into cobalt ferrite was found to reduce the magnetocrystalline anisotropy and hence the susceptibility is increased. Under axial compressive stresses, χD0 and χS0 of all samples decrease. The Mn-substituted samples with x = 0.2 and 0.3 show larger reductions in χD0 and χS0 than the pure cobalt ferrite. The stress effects on χS0 and the dependence of the magnetomechanical effect on Mn content were reproduced in model calculations by taking into account the combined effects of stress-induced and magnetocrystalline anisotropies on magnetization rotation.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Lm Deformation, plasticity, and creep
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy
75.50.Gg Ferrimagnetics
75.60.Ch Domain walls and domain structure
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