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15 May 2005

Volume 97, Issue 10, Articles (10xxxx)

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back to top Special Materials: Magneto-Optic, Magnetocaloric, and Magnetoelastic Materials

Stress annealing of Fe–Ga transduction alloys for operation under tension and compression

M. Wun-Fogle, J. B. Restorff, A. E. Clark, Erin Dreyer, and Eric Summers

J. Appl. Phys. 97, 10M301 (2005); http://dx.doi.org/10.1063/1.1845933 (3 pages) | Cited 9 times

Online Publication Date: 13 May 2005

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The addition of Ga to bcc α‐Fe increases the magnetostriction of Fe in the [100] direction (a factor of 12 for Fe81Ga19). The effect of annealing highly textured polycrystalline Fe81.6Ga18.4 rods under compressive stresses of −100 and −150 MPa for 10–100 min at temperatures between 625 °C and 635 °C was examined. After annealing, all samples showed nearly full performance at near-zero stresses. Samples annealed with −100 MPa stress maintained a high magnetostriction up to ∼ 20 MPa tensile stress; the sample annealed with −150 MPa stress maintained its magnetostriction up to ∼ 30 MPa.
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75.50.Bb Fe and its alloys
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Gw Magnetic anisotropy
81.40.Gh Other heat and thermomechanical treatments
81.05.Bx Metals, semimetals, and alloys

Model for the elastic behavior near intermartensitic transitions

Liyang Dai, James Cullen, and Manfred Wuttig

J. Appl. Phys. 97, 10M302 (2005); http://dx.doi.org/10.1063/1.1845975 (3 pages)

Online Publication Date: 13 May 2005

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Transitions between different martensitic states have been observed in Ni0.50Mn0.284Ga0.216 using elastic constant measurements. In this paper, we develop a model to explain the reentrant behavior based on a Landau expansion of the free energy in strain space. Here, we assume that the coefficient of the third-order term as well as the second-order term has significant temperature dependence. This assumption results in a C′ versus temperature in good agreement with observation. The model and possible modifications to it are discussed and compared to the elastic constant data.
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81.30.Kf Martensitic transformations
81.40.Jj Elasticity and anelasticity, stress-strain relations
64.70.K- Solid-solid transitions
65.40.G- Other thermodynamical quantities
62.20.D- Elasticity

Magnetocaloric effect in itinerant electron metamagnetic systems La(Fe1−xCox)11.9Si1.1

F. X. Hu, J. Gao, X. L. Qian, Max Ilyn, A. M. Tishin, J. R. Sun, and B. G. Shen

J. Appl. Phys. 97, 10M303 (2005); http://dx.doi.org/10.1063/1.1847071 (3 pages) | Cited 10 times

Online Publication Date: 13 May 2005

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The NaZn13-type compounds La(Fe1−xCox)11.9Si1.1 (x = 0.04, 0.06, 0.08) were successfully synthesized, in which the Si content is the limit that can be reached by arc-melting technique. TC is tunable from 243 to 301 K with Co doping from x = 0.04 to 0.08. Great magnetic entropy change ΔS in a wide temperature range from ∼ 230 to ∼ 320 K has been observed. The adiabatic temperature change ΔTad upon changing magnetic field was also directly measured. ΔTad of sample x = 0.06 reaches ∼ 2.4 K upon a field change from 0 to 1.1 T. The temperature hysteresis upon phase transition is small, ∼ 1 K, for all samples. The influence of Co doping on itinerant electron metamagnetic transition and magnetic entropy change is discussed.
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75.50.Dd Nonmetallic ferromagnetic materials
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
65.40.G- Other thermodynamical quantities

The structural and magnetic properties of Ni2Mn1−xMxGa (M = Co, Cu)

Mahmud Khan, Igor Dubenko, Shane Stadler, and Naushad Ali

J. Appl. Phys. 97, 10M304 (2005); http://dx.doi.org/10.1063/1.1847131 (3 pages) | Cited 24 times

Online Publication Date: 13 May 2005

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In Ni2MnGa (cubic structure of L21 type) a first order martensitic structural transition, from the parent cubic (austenitic) phase to a low temperature complex tetragonal structure, takes place at TM = 202 K, and ferromagnetic order in the austenitic phase sets at TC = 376 K. In this work, the Mn sites in Ni2MnGa have been partially substituted with magnetic Co and nonmagnetic Cu, and the influence of these substitutions on the structural and magnetic properties of Ni2Mn1−xMxGa (M = Co and Cu) have been studied by XRD and magnetization measurements. X-ray diffraction patterns indicate that the Co doped system possess a highly ordered Heusler alloy L21 type structure for 0.05<x<0.12, and the Cu doped compounds possess L21 structure for 0.05<x<0.10. The ferromagnetic ordering temperature increases with increasing Co concentration for this system, and rapidly decreases with increasing Cu concentration. Both systems show the increase in TM with increasing Co and Cu concentration. (T-x) phase diagrams have been plotted. The results are discussed in terms of 3d-electron concentration variation.
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75.50.Cc Other ferromagnetic metals and alloys
81.30.Kf Martensitic transformations
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.70.K- Solid-solid transitions
61.72.S- Impurities in crystals

Large magnetocaloric effect in melt-spun LaFe13−xSix

O. Gutfleisch, A. Yan, and K.-H. Müller

J. Appl. Phys. 97, 10M305 (2005); http://dx.doi.org/10.1063/1.1847871 (3 pages) | Cited 36 times

Online Publication Date: 13 May 2005

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A very large value of magnetic entropy change ∣ΔS∣ = 31 J/kg K was obtained at 201 K under 5 T in LaFe11.8Si1.2 melt-spun ribbons subjected to a very short-time annealing (2 h/1050 °C). This value is much higher than that of a bulk LaFe11.44Si1.56 in this temperature range. The large ∣ΔS∣ is attributed to the first-order thermally induced transition at the Curie temperature TC, and is enhanced even further due to a more homogenous element distribution. With increasing Si concentration, TC is increased and ∣ΔS∣ is decreased due to a weakening or an even disappearance of the first-order magnetic phase transition.
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75.50.Bb Fe and its alloys
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.40.Gh Other heat and thermomechanical treatments

Large magnetocaloric effect in single crystal Pr0.63Sr0.37MnO3

Manh-Huong Phan, Hua-Xin Peng, and Seong-Cho Yu

J. Appl. Phys. 97, 10M306 (2005); http://dx.doi.org/10.1063/1.1849554 (3 pages) | Cited 6 times

Online Publication Date: 13 May 2005

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This article reports the magnetocaloric effect in a single crystal Pr0.63Sr0.37MnO3, which undergoes a very sharp ferromagnetic-to-paramagnetic phase transition at ∼ 300 K. A large magnetic entropy change of 8.52 J/kg K and a large adiabatic temperature change of 5.65 K for an applied field change of 50 kOe were observed around 300 K; this allows water to be used as a heat transfer fluid in the room-temperature magnetic refrigeration regime. The distribution of entropy change (ΔSM) was found to be very uniform and which is desirable for an Ericson-cycle magnetic refrigerator. The large magnetic entropy change induced by a relatively low magnetic field change is beneficial for household application.
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75.50.Dd Nonmetallic ferromagnetic materials
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
65.40.G- Other thermodynamical quantities

Structure and magnetic properties of mechanically alloyed Tb0.7Pr0.3(Fe0.9B0.1)1.93 and the magnetostriction of its epoxy composites

J. J. Liu, W. J. Ren, X. G. Zhao, W. Liu, and Z. D. Zhang

J. Appl. Phys. 97, 10M307 (2005); http://dx.doi.org/10.1063/1.1851751 (3 pages) | Cited 1 time

Online Publication Date: 13 May 2005

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The C15 Laves phase with composition Tb0.7Pr0.3(Fe0.9B0.1)1.93 has been synthesized by mechanical alloying and subsequent annealing process. The structure and magnetic properties of Tb0.7Pr0.3(Fe0.9B0.1)1.93 have been investigated. The effect of the annealing on the magnetic properties has been studied. The samples annealed at 773 K are found to have a coercivity of 6.66 kOe at room temperature. The coercivity decreases monotonically with increase in the annealing temperature. The epoxy/Tb0.7Pr0.3(Fe0.9B0.1)1.93 composites have been produced by a cold compression-molding technique. The magnetostriction of the epoxy/Tb0.7Pr0.3(Fe0.9B0.1)1.93 composites with different weight ratios of epoxy resin to powder is measured by a standard strain technique. The Tb0.7Pr0.3(Fe0.9B0.1)1.93 composites, with a weight ratio of epoxy resin to powder of 5:100, have a high magnetostriction of 810 ppm, at an applied magnetic field of 12 kOe. The Tb0.7Pr0.3(Fe0.9B0.1)1.93 alloy combines a high magnetostriction with a low coercivity, which is a promising magnetostrictive material.
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75.50.Bb Fe and its alloys
81.05.Bx Metals, semimetals, and alloys
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.66.Dk Alloys
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.40.Gh Other heat and thermomechanical treatments
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Dynamic magnetomechanical properties of Terfenol-D/epoxy pseudo 1-3 composites

Siu Wing Or, Tongle Li, and Helen Lai Wa Chan

J. Appl. Phys. 97, 10M308 (2005); http://dx.doi.org/10.1063/1.1851889 (3 pages) | Cited 23 times

Online Publication Date: 16 May 2005

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Terfenol-D/epoxy pseudo 1-3 composites were fabricated by embedding and aligning Terfenol-D particles with a size distribution of 10–300 μm in a passive epoxy matrix using six Terfenol-D volume fractions (υf) ranging from 0.22 to 0.72. The dependence of the dynamic relative permeability (μr33T), elastic modulus (E3H), and dynamic strain coefficient (d33) on υf was investigated as a function of magnetic bias field (HBias). The HBias response data showed that the built-in non-180° domain states related to residual compressive stresses in the composites result in a significant decrease in μr33T for HBias<40 kA/m in addition to a minimization of E3H and a maximization of d33 near HBias = 40 kA/m. The υf dependent data revealed that μr33T is almost a linear function of υf; E3H increases gradually with increasing υf; and d33 increases initially, leveling off for υf>0.5. The present study provides a useful guide to optimize the composite properties for transducer design.
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81.05.Qk Reinforced polymers and polymer-based composites
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Jj Elasticity and anelasticity, stress-strain relations
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
62.20.D- Elasticity
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure

Magnetocaloric effect in NiMnGa particles produced by spark erosion

Y. J. Tang, Virgil C. Solomon, D. J. Smith, H. Harper, and A. E. Berkowitz

J. Appl. Phys. 97, 10M309 (2005); http://dx.doi.org/10.1063/1.1852451 (3 pages) | Cited 5 times

Online Publication Date: 16 May 2005

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The magnetic entropy change of tetragonal and orthorhombic NiMnGa fine particles made by spark erosion was investigated in this paper. It was found that the structure and crystalline phase transformation temperatures can be strongly affected by the compositions of the particles, while Curie temperature is less sensitive to the compositions. Due to the possible distribution of the particle size and compositions in these particles, the magnetic entropy changes observed are much broader and smaller than those of bulk NiMnGa alloys. The maximum absolute value of entropy change ΔS = 2 J Kg−1 K−1 was observed for tetragonal structure NiMnGa particles at 95 °C in a field of 2 T.
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75.50.Cc Other ferromagnetic metals and alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Kf Martensitic transformations
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
65.40.G- Other thermodynamical quantities
64.70.K- Solid-solid transitions
61.66.Dk Alloys

Analysis of magnetization and magnetocaloric effect in amorphous FeZrMn ribbons

S. G. Min, K. S. Kim, S. C. Yu, H. S. Suh, and S. W. Lee

J. Appl. Phys. 97, 10M310 (2005); http://dx.doi.org/10.1063/1.1853193 (3 pages) | Cited 14 times

Online Publication Date: 16 May 2005

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The magnetization behaviors have been measured for amorphous Fe90−xMnxZr10 (x = 8 and 10) alloys. The Curie temperature is decreased from 210 K to 185 K with increasing Mn concentration (x = 8 to x = 10). The magnetization measurements were conducted at temperatures above the Curie temperature in the paramagnetic region. In both samples, the magnetic properties showed superparamagnetic behavior above Tc where the mean magnetic moment of the superparamagnetic spin clusters decreased with increasing temperature. A large magnetic entropy change ΔSM, which is calculated from H vs M curves associated with the ferromagnetic-paramagnetic transitions in amorphous, has been observed. The maximum ΔSM of Fe82Mn8Zr10 is 2.87 J/kg K at 210 K for an applied field of 5 T. The peak of magnetic entropy change was observed at the Curie temperature. The ΔSM decreases with increasing Mn concentration to 2.33 J/kg K.
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75.50.Bb Fe and its alloys
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.20.En Metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Sg Magnetocaloric effect, magnetic cooling
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
75.30.Cr Saturation moments and magnetic susceptibilities

Enhancement of polar Kerr effect by forming Au nanoparticles on Ni surface

S. U. Jen and K. C. Chen

J. Appl. Phys. 97, 10M311 (2005); http://dx.doi.org/10.1063/1.1854311 (3 pages) | Cited 1 time

Online Publication Date: 16 May 2005

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Au(x)/Ni(y)/glass(sub) bilayered films, with x ranging from 0 to 310 Å and y = 85 Å, were made by the vapor evaporation method in vacuum. The surface morphology of each bilayer was examined by an atomic force microscope. The results show that when x = xm = 25 and 100 Å, respectively, there were, in particular, a large number of Au nanoparticles (or nanoislands) forming on top of the Ni surface. As a result, we observed considerable enhancement in either the polar Kerr rotation θK or the extraordinary Hall coefficient RS at these two thicknesses. As is well known, the penetration depth δP of the electron transverse flow, crossing the Au/Ni interface from the Ni to the Au layer, is of the order of the electron mean free path ℓAu, i.e., δP = (3/8)ℓAu ≈ 116 Å, in the Au layer. Hence, the situation xm<δP is always satisfied. Then, the strong enhancement of θK is due to the surface plasma resonance effect on the Au nanoparticles (e.g., by reducing the real part of the diagonal dielectric tensor εxx so that Re[εxx(ω)] ≈ 1, where ℏω = 1.96 eV). Moreover, the formation of Au nanoparticles roughens the bilayer’s surface. That means the enhancement of RS is due to the increase of the surface resistivity ρS. Finally, since the side-jump mechanism is effective, it could affect θK too (e.g., by enhancing the imaginary part of the off-diagonal conductivity Im[σxy]).
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75.50.Cc Other ferromagnetic metals and alloys
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.20.Ls Magneto-optical effects
78.20.Ek Optical activity
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.25.+i Surface conductivity and carrier phenomena
73.40.Jn Metal-to-metal contacts
72.15.Lh Relaxation times and mean free paths
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.37.Ps Atomic force microscopy (AFM)

Ferromagnetic shape memory alloys: Theory of interactions

D. I. Paul, R. C. O’Handley, and Bradley Peterson

J. Appl. Phys. 97, 10M312 (2005); http://dx.doi.org/10.1063/1.1854871 (3 pages) | Cited 4 times

Online Publication Date: 16 May 2005

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Twin boundary motion in a viscous discrete lattice is examined in the presence of a dislocation defect and a magnetic driving force supplemented by an acoustical signal. The results show, amongst others, a resistance to twin boundary motion due to lattice discreteness and a large but temporary reduction in twin boundary velocity during the interaction between the localized pulse and the dislocation.
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75.50.Bb Fe and its alloys
75.50.Cc Other ferromagnetic metals and alloys
61.72.Bb Theories and models of crystal defects
75.40.Mg Numerical simulation studies
61.72.Yx Interaction between different crystal defects; gettering effect
81.05.Bx Metals, semimetals, and alloys
61.72.Mm Grain and twin boundaries
81.30.Kf Martensitic transformations
64.70.K- Solid-solid transitions

Magnetic anisotropy and phase transitions in single-crystal Tb5(Si2.2Ge1.8)

M. Han, J. E. Snyder, W. Tang, T. A. Lograsso, D. L. Schlagel, and D. C. Jiles

J. Appl. Phys. 97, 10M313 (2005); http://dx.doi.org/10.1063/1.1855196 (3 pages) | Cited 2 times

Online Publication Date: 16 May 2005

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The Tb5(SixGe4−x) alloy system has many features in common with the Gd5(SixGe4−x) system although it has a more complex magnetic and structural phase diagram. This paper reports on the magnetic anisotropy and magnetic phase transition of single-crystal Tb5(Si2.2Ge1.8) which has been investigated by the measurements of M-H and M-T along the a, b, and c axes. The variation of 1/χ vs T indicates that there is a transition from paramagnetic to ferromagnetic at Tc = 110 K. Below this transition temperature M-H curves show very strong anisotropy, and it is believed that this is due to the complex spin configuration. M-H measurements at T = 110 K show that the a axis is the easy axis, and that the saturation magnetization is 200 emu/g. The b axis is the hard axis, which needs an external magnetic field much higher than 2 T to saturate the magnetization in that direction, indicating a high magnetocrystalline anisotropy. The c axis is of intermediate hardness. The magnetic properties of this material are therefore very different from those of the related Gd5Si2Ge2 system, in which the b axis was found to be the easy axis and the magnitude of the anisotropy was smaller.
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75.50.Cc Other ferromagnetic metals and alloys
75.20.En Metals and alloys
75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities

Magnetization and neutron diffraction studies on Dy5Si2Ge2

R. Nirmala, V. Sankaranarayanan, K. Sethupathi, A. V. Morozkin, Q. Cai, Z. Chu, J. B. Yang, W. B. Yelon, and S. K. Malik

J. Appl. Phys. 97, 10M314 (2005); http://dx.doi.org/10.1063/1.1855646 (3 pages) | Cited 1 time

Online Publication Date: 16 May 2005

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The compound Dy5Si2Ge2 crystallizes in an orthorhombic structure (Sm5Ge4 type, space group Pnma). Magnetization measurements performed in the temperature range of 2–300 K in applied fields up to 7 T reveal that this compound orders antiferromagnetically at 56 K (TN) but with a positive paramagnetic Curie temperature θP. Magnetization-field isotherms, obtained at 5 K and 20 K, display a field-induced antiferromagnetic to ferromagnetic transition. The magnetization approaches saturation in a field of 6 T with a moment value of ∼ 8μB/Dy3+. Neutron diffraction measurements, carried out at 9.2 K, suggest that Dy moments arrange spirally along the a axis giving rise to a canted antiferromagnetic structure. The analysis of neutron diffraction data yields an ordered state magnetic moment of 7.63μB per Dy3+ ion.
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75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.30.Cr Saturation moments and magnetic susceptibilities
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Magnetic field dependence of galfenol elastic properties

G. Petculescu, K. B. Hathaway, T. A. Lograsso, M. Wun-Fogle, and A. E. Clark

J. Appl. Phys. 97, 10M315 (2005); http://dx.doi.org/10.1063/1.1855711 (3 pages) | Cited 35 times

Online Publication Date: 16 May 2005

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Elastic shear moduli measurements on Fe100−xGax (x = 12–33) single crystals (via resonant ultrasound spectroscopy) with and without a magnetic field and within 4–300 K are reported. The pronounced softening of the tetragonal shear modulus c′ is concluded to be, based on magnetoelastic coupling, the cause of the second peak in the tetragonal magnetostriction constant λ100 near x = 28. Exceedingly high ΔE effects ( ∼ 25%), combined with the extreme softness in c′ (c′<10 GPa), suggest structural changes take place, yet, gradual in nature, as the moduli show a smooth dependence on Ga concentration, temperature, and magnetic field. Shear anisotropy (c44/c′) as high as 14.7 was observed for Fe71.2Ga28.8.
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75.50.Bb Fe and its alloys
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Temperature dependence of the magnetic anisotropy and magnetostriction of Fe100−xGax (x = 8.6, 16.6, 28.5)

A. E. Clark, M. Wun-Fogle, J. B. Restorff, K. W. Dennis, T. A. Lograsso, and R. W. McCallum

J. Appl. Phys. 97, 10M316 (2005); http://dx.doi.org/10.1063/1.1856731 (3 pages) | Cited 19 times

Online Publication Date: 16 May 2005

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The temperature dependence of the lowest order magnetic anisotropy constant K1 and the lowest order saturation magnetostriction constant, (3/2)λ100, were measured from 4 K to 300 K for Fe91.4Ga8.6,Fe83.4Ga16.6, and Fe71.5Ga28.5 and were compared to the normalized magnetization power law, ml(l+1)/2. Fe91.4Ga8.6 maintains the magnetostriction anomaly of Fe (dλ100/dT>0) and K1 is a reasonable fit to the ml(l+1)/2 power law with K1(0 K) ≅ 90 kJ/m3. Fe83.4Ga16.6 does not show a magnetostriction anomaly, but fits the power law remarkably well. Fe71.5Ga28.5 possesses a small K1( ∼ 1 kJ/m3) at all temperatures and a large temperature dependent magnetostriction, reaching ∼ 800 ppm at low temperature.
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75.50.Bb Fe and its alloys
75.30.Gw Magnetic anisotropy
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetocaloric effect of La0.8Sr0.2MnO3 compound under pressure

Daniel L. Rocco, R. Almeida Silva, A. Magnus G. Carvalho, Adelino A. Coelho, José P. Andreeta, and Sergio Gama

J. Appl. Phys. 97, 10M317 (2005); http://dx.doi.org/10.1063/1.1856891 (3 pages) | Cited 7 times

Online Publication Date: 16 May 2005

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The La0.8Sr0.2MnO3 compound presents a ferromagnetic paramagnetic transition around room temperature to which a reasonably high magnetocaloric effect is associated, turning this material of interest for application in magnetic refrigeration. We synthesized this compound in fiber single crystalline form by the Laser Heated Pedestal Growth method. The sample was characterized by x-ray diffraction and magnetic measurements as a single phase and with the required magnetic properties. We measured the magnetic properties and the magnetocaloric effect under hydrostatic pressure for pressures up to 6 kbar as a function of temperature. Our results indicate that the Curie temperature increases with pressure while the low temperature transition from the orthorhombic to the rhombhoedral structures decreases as pressure increases. This is in close agreement with the literature. Measurement of the magnetocaloric effect at the high temperature transition indicates that the peak of the effect follows the trend of the Curie temperature, but its maximum value remains almost constant as a function of pressure.
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75.50.Dd Nonmetallic ferromagnetic materials
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Measurement of field-dependence elastic modulus of iron–gallium alloy using tensile test

Jin-Hyeong Yoo and Alison B. Flatau

J. Appl. Phys. 97, 10M318 (2005); http://dx.doi.org/10.1063/1.1857392 (3 pages) | Cited 3 times

Online Publication Date: 16 May 2005

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An experimental approach is used to identify Galfenol material properties under dc magnetic bias fields. Dog-bone-shaped specimens of single crystal Fe100−xGax, where 18.6 ⩽ x ⩽ 33.2, underwent tensile testing along two crystallographic axis orientations, [110] and [100]. Young’s modulus and Poisson’s ratio sensitivity to magnetic fields and stoichiometry are investigated. Data are presented that demonstrate the dependence of these properties on applied magnetic-field levels and provide a substantial assessment of the trends in material properties for performance of alloys of different stoichiometries under varied operating conditions.
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75.50.Bb Fe and its alloys
81.05.Bx Metals, semimetals, and alloys
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
61.66.Bi Elemental solids
61.66.Dk Alloys
81.70.Bt Mechanical testing, impact tests, static and dynamic loads

Large energy absorption in Ni–Mn–Ga/polymer composites

Jorge Feuchtwanger, Marc L. Richard, Yun J. Tang, Ami E. Berkowitz, Robert C. O’Handley, and Samuel M. Allen

J. Appl. Phys. 97, 10M319 (2005); http://dx.doi.org/10.1063/1.1857653 (3 pages) | Cited 17 times

Online Publication Date: 16 May 2005

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Ferromagnetic shape memory alloys can respond to a magnetic field or applied stress by the motion of twin boundaries and hence they show large hysteresis or energy loss. Ni–Mn–Ga particles made by spark erosion have been dispersed and oriented in a polymer matrix to form pseudo 3:1 composites which are studied under applied stress. Loss ratios have been determined from the stress-strain data. The loss ratios of the composites range from 63% to 67% compared to only about 17% for the pure, unfilled polymer samples.
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75.50.Cc Other ferromagnetic metals and alloys
81.05.Ni Dispersion-, fiber-, and platelet-reinforced metal-based composites
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
61.72.Mm Grain and twin boundaries

The magnetic and magnetocaloric properties of Gd5Ge2Si2 compound under hydrostatic pressure

A. Magnus G. Carvalho, Cleber S. Alves, Ariana de Campos, Adelino A. Coelho, Sergio Gama, Flavio C. G. Gandra, Pedro J. von Ranke, and Nilson A. Oliveira

J. Appl. Phys. 97, 10M320 (2005); http://dx.doi.org/10.1063/1.1860932 (3 pages) | Cited 21 times

Online Publication Date: 16 May 2005

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The Gd5Ge2Si2 compound presents a giant magnetocaloric effect with transition temperature at around 276 K and is a very good candidate for application as an active regenerator material in room temperature magnetic refrigerators. Recently it has been shown that pressure induces a colossal magnetocaloric effect in MnAs, a material that presents a giant magnetocaloric effect and a strong magnetoelastic coupling, as also happens with the Gd5Ge2Si2 compound. This motivated a search of the colossal effect in the Gd5Ge2Si2 compound. This work reports our measurements on the magnetic properties and the magnetocaloric effect of Gd5Ge2Si2 under hydrostatic pressures up to 9.2 kbar and as a function of temperature. Contrary to what happens with MnAs, pressure increases the Curie temperature of the compound, does not affect the saturation magnetization and decreases markedly its magnetocaloric effect.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Kerr measurements on single-domain SrRuO3 thin films

G. Herranz, N. Dix, F. Sánchez, B. Martínez, J. Fontcuberta, M. V. García-Cuenca, C. Ferrater, M. Varela, D. Hrabovsky, and A. R. Fert

J. Appl. Phys. 97, 10M321 (2005); http://dx.doi.org/10.1063/1.1861552 (3 pages) | Cited 4 times

Online Publication Date: 16 May 2005

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We report on the magneto-optical measurements of an epitaxial SrRuO3 film grown on SrTiO3 (0 0 1), which previously was determined to be single domain orientated by x-ray diffraction and Raman spectroscopy techniques. Our experiments reveal a large Kerr rotation, which reaches a maximum value of about 0.5° at low temperature. By measuring magnetic hysteresis loops at different temperatures, we determined the temperature dependence of the Kerr rotation in the polar configuration. Values of the anisotropic magnetoresistance ∼ 20% have been measured. These values are remarkably higher than those of other metallic oxides such as manganites. This striking difference can be attributed to the strong spin-orbit interaction of the Ru 4d ion in the SrRuO3 compound.
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75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
68.55.-a Thin film structure and morphology
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.47.Pq Other materials
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
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