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7 May 2013

Volume 113, Issue 17, Articles (17xxxx)

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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 New Magnetic Materials, Instrumentation, and Measurement Techniques

Structural and magnetic properties of the Heusler compound Fe2MnGa

Teuta Gasi, Ajaya K. Nayak, Michael Nicklas, and Claudia Felser

J. Appl. Phys. 113, 17E301 (2013); http://dx.doi.org/10.1063/1.4794979 (3 pages)

Online Publication Date: 12 March 2013

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We report a structural and magnetization study of the Heusler compound Fe2MnGa. The sample shows a single cubic phase with a large Curie temperature (TC) of 750 K. The sample undergoes a disorder induced first-order ferromagnetic (FM) to antiferromagnetic (AFM) transition around the room temperature. This transition results in a mixed AFM and FM phases. A large exchange bias (EB) of 0.12 T is observed for a cooling field of 0.5 T. The EB decreases to a near saturation value of 0.07 T for a cooling field of 7 T. The ac-susceptibility measurements confirm that no spin-glass type of magnetic state is present in the sample.
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61.66.Dk Alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Bb Fe and its alloys
75.30.Cr Saturation moments and magnetic susceptibilities

Magnetic and structural properties of the new double perovskite family Sr2GdRu1−xRexOy

L. T. Corredor, J. Roa-Rojas, D. A. Landínez Téllez, R. Beltrán, P. Pureur, F. Mesquita, and J. Albino Aguiar

J. Appl. Phys. 113, 17E302 (2013); http://dx.doi.org/10.1063/1.4796045 (3 pages)

Online Publication Date: 22 March 2013

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We study the synthesis and structural and magnetic characterization of the new compound family Sr2GdRu1−xRexOy, with doping levels at 3%, 6%, 9%, and 12%. X-ray diffractograms revealed that the samples crystallize in a monoclinic structure, and exhibit a strong distortion of the octahedron Ru(Re)O6/GdO6 lattice. Magnetic characterization revealed non-ideal antiferromagnetic behavior, with Néel temperatures close to 25 K, and an interesting metamagnetic feature below applied magnetic fields between 1.0 and 1.4 T. The existence of a Re doping level limit that favors an ideal antiferromagnetic character of the perovskite is discussed.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Ee Antiferromagnetics
61.66.Fn Inorganic compounds

Interplay of 3d-4f exchange interaction in Pr0.5-xNdxSr0.5CoO3

Pawan Kumar, M. Aparnadevi, and R. Mahendiran

J. Appl. Phys. 113, 17E303 (2013); http://dx.doi.org/10.1063/1.4798503 (3 pages)

Online Publication Date: 3 April 2013

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We have investigated electrical and magnetic properties of Pr0.5-xNdxSr0.5CoO3 (x = 0.0, 0.1, 0.2, 0.3, and 0.5) samples. Upon cooling, field-cooled magnetization of Pr0.5Sr0.5CoO3 shows an anomalous increase at TA = 120 K within the ferromagnetic state coupled structural and magnetic anisotropy transitions. This anomaly shifts to 88 K for x = 0.1 but its magnetization starts decreasing below Tferri = 35 K, where Tferri signals the onset of ferrimagnetic interaction between Nd(4f) and Co(3d) moments. The structural transition is absent in x ≥ 0.2. While the ferromagnetic Curie temperature decreases with increasing Nd content by 8 K, Tferri increases from 35 K for x = 0.1 to 80 K for x = 0.5. The ferrimagnetic interaction does not affect the dc resistivity. All the studied samples are metallic and magnetoresistance decreases from −6.7% for x = 0 to −0.7% for x = 0.5.
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75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys
75.50.Gg Ferrimagnetics
75.30.Cr Saturation moments and magnetic susceptibilities

A muon spin relaxation study of the metal-organic magnet Ni(TCNQ)2

Adam Berlie, Ian Terry, Sean Giblin, Tom Lancaster, and Marek Szablewski

J. Appl. Phys. 113, 17E304 (2013); http://dx.doi.org/10.1063/1.4798616 (3 pages)

Online Publication Date: 3 April 2013

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An investigation of the magnetism of the deuterated form of the metal-organic ferromagnet Ni(TCNQ)2 using the muon spin relaxation technique, is reported. Ni(TCNQ-D4)2 was synthesized in a similar manner to the protio-form, and the crystalline product formed was found to have a Curie temperature of TC = 20 K. This transition temperature was 18% larger than that of the protio-form synthesized in our laboratory. Muon spin relaxation measurements were performed in Zero Field (ZF) and in Longitudinal Fields (LF) of up to 0.45 T. The ZF data confirmed that the sample undergoes a bulk ferromagnetic transition at a temperature similar to that observed by the bulk magnetization data. However, ZF measurements also showed that another transition occurs below approximately 6 K, which is believed to be a transition to a magnetic glassy state. The LF results indicate that a significant dynamical component to the magnetism is present below TC as LF fields up to 0.45 T cannot completely re-polarise the spins of the implanted muons. Moreover, at 5 mT, the data can be fit using a damped oscillatory function. Taken together, the ZF and LF results suggest the presence of two dominant sites for implanted muons, one of which is strongly coupled to the bulk magnetic transition and the other that is more weakly coupled and has a dynamical magnetic environment below TC. Such a situation may be a consequence of muon spin relaxation probing core and surface magnetic environments of nanoparticles or clusters.
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76.75.+i Muon spin rotation and relaxation
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Rf Surface magnetism

Origin of ferromagnetism in BaTiO3 nanoparticles prepared by mechanical milling

The-Long Phan, P. Zhang, D. S. Yang, T. D. Thanh, D. A. Tuan, and S. C. Yu

J. Appl. Phys. 113, 17E305 (2013); http://dx.doi.org/10.1063/1.4799473 (3 pages)

Online Publication Date: 3 April 2013

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Recent studies have pointed out an existence of the room-temperature ferromagnetism in nanostructured BaTiO3 materials. It has been thought that the ferromagnetism is due to intrinsic defects. To elucidate this issue, we have prepared BaTiO3 nanoparticles by mechanical milling, starting from diamagnetic/nonmagnetic BaTiO3 powders, and then investigated their magnetic properties. Our idea is motivated by the fact that the mechanical milling introduces more lattice defects to a ground material. If so, the ferromagnetic (FM) order will increase with increasing the density of defects. Here, the defect density can be changed upon the milling time (tm). Our magnetic measurements at 300 K have indicated that the FM order increases with increasing tm as expected. To understand the nature of ferromagnetism, we studied X-ray absorption fine structure (XAFS) spectra of the samples for the Ti K-edge. The shift of the absorption edge towards lower energies of Ti3+ with increasing tm, proving an increase in Ti3+ concentration, was found. Detailed studies and analyses of XAFS and electron-spin-resonance spectra give the evidence that the ferromagnetism in BaTiO3 nanoparticles is due to intrinsic defects, in which oxygen vacancies and interstitials, and Ti3+ created during the milling play decisive role.
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75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
78.70.Dm X-ray absorption spectra
81.16.Rf Micro- and nanoscale pattern formation
61.72.jd Vacancies
61.72.jj Interstitials

Mössbauer analysis of silicate Li2FeSiO4 and delithiated Li2−xFeSiO4 (x = 0.66) compounds

In Kyu Lee, Sam Jin Kim, Taejoon Kouh, and Chul Sung Kim

J. Appl. Phys. 113, 17E306 (2013); http://dx.doi.org/10.1063/1.4799153 (3 pages)

Online Publication Date: 4 April 2013

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Lithium iron silicate compounds of Li2FeSiO4 and partially delithiated Li2−xFeSiO4 (x = 0.66) were synthesized by vacuum-sealed solid-state and chemical delithiation reactions, and their magnetic properties were characterized based on Mössbauer analysis. Crystal structures of both Li2FeSiO4 and Li2−xFeSiO4 (x = 0.66) compounds are found to be γs-type (P21/n) monoclinic structures with difference in the lattice parameters due to lithium delithiation. Mössbauer spectrum of Li2FeSiO4 below TN1 = 20 K exhibits eight Lorentzians of Fe2+ with antiferromagnetic ordering. However, the spectrum of intermediate Li2−xFeSiO4 (x = 0.66) compound shows the appearance of magnetically ordered Fe3+ sextet below TN2 = 28 K. The temperature-dependent isomer shift of Li2−xFeSiO4 indicates the coexistence of nonequivalent Fe2+/Fe3+ valence states with the partial oxidation of FeO4, enhanced by the lithium ion deficiency. Also, we have observed a considerable change in electric quadrupole interaction between Fe2+/Fe3+ ions in Li2−xFeSiO4, when compared to that of Li2FeSiO4, due to the different lattice and valence electron contributions, being originated from crystalline and valence transitions caused by the lithiation/delithiation process.
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76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.66.Fn Inorganic compounds
82.30.-b Specific chemical reactions; reaction mechanisms
75.50.Ee Antiferromagnetics
81.10.Dn Growth from solutions
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Magnetic Compton scattering studies of magneto-dielectric Ba(Co0.85Mn0.15)O3−δ

R. Shinoda, M. Itou, Y. Sakurai, H. Yamamoto, N. Hirao, Y. Baba, A. Iwase, and T. Matsui

J. Appl. Phys. 113, 17E307 (2013); http://dx.doi.org/10.1063/1.4799476 (3 pages)

Online Publication Date: 9 April 2013

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We revealed that the Ba(Co0.85Mn0.15)O3−δ ceramic samples exhibited ferromagnetic-dielectric behavior below the magnetic transition temperature of about 35 K. The origin of their magnetic ordering was expected to super-exchange coupling of Co4+(d5)-O2−-Mn4+(d3) with bonding angle of 180° and/or Mn4+(d3)-O2−-Mn4+(d3) with bonding angle of 90°. The magnetic spin momentum estimated by the magnetic Compton profiles (MCP) of the samples had similar temperature dependence as that determined by the temperature dependence of magnetic moment by superconducting quantum interference device, which meant that the observed magnetic moments could be ascribed to the spin moment. The shapes of the MCPs of the samples were completely same regardless of the temperature measured. This result indicates that there are no changes of the momentum space distribution of spin density between ferromagnetic and paramagnetic states. So, this magnetic transition is simply caused by a thermal fluctuation of the spin.
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75.30.Et Exchange and superexchange interactions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.85.+t Magnetoelectric effects, multiferroics
75.30.Ds Spin waves
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Cr Saturation moments and magnetic susceptibilities

Kinetic arrest related to a first-order ferrimagnetic to antiferromagnetic transition in the Heusler compound Mn2PtGa

Ajaya K. Nayak, Michael Nicklas, Chandra Shekhar, and Claudia Felser

J. Appl. Phys. 113, 17E308 (2013); http://dx.doi.org/10.1063/1.4800687 (3 pages)

Online Publication Date: 10 April 2013

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We report a magnetization study of the Heusler compound Mn2PtGa that shows the existence of a magnetic-glass state. Mn2PtGa shows a first-order ferromagnetic (FM)/ferrimagnetic (FI) to antiferromagnetic (AFM) transition in contrast to the martensitic structural transition observed in several Heusler alloys. The kinetic arrest of this first-order FM (FI) to AFM transition leads to the observed magnetic-glass behavior. We show that the strength of the applied magnetic field, which is the primary parameter to induce the magnetic-glass state, is also responsible for the stability of the supercooled FM (FI) phase in time.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.50.Gg Ferrimagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Ferromagnetism in Mn half-doped LaCrO3 perovskite

Petrucio Barrozo and J. Albino Aguiar

J. Appl. Phys. 113, 17E309 (2013); http://dx.doi.org/10.1063/1.4801507 (3 pages)

Online Publication Date: 19 April 2013

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In this work, we present results on the structural, electrical, and magnetic properties of pure and half-doped LaCrO3 compounds. It is observed that including Mn the lattice structure changes from orthorhombic to rhombohedral. The electrical transport in LaCrO3 can be described by a band gap model, whereas in La2CrMnO6, a charge localization occurs and the electrical transport is described by a variable range hopping model. The magnetic measurements show that LaCrO3 is a G-type antiferromagnetic with a Neel temperature at 290 K, and the Mn doping favors the ferromagnetic order and reduces the transition temperature.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
72.20.Ee Mobility edges; hopping transport
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
75.50.Dd Nonmetallic ferromagnetic materials
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