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30 Jan 2012

Volume 100, Issue 5, Articles (05xxxx)

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Appl. Phys. Lett. 100, 053101 (2012); http://dx.doi.org/10.1063/1.3679127 (3 pages)

Shinya Kano, Yasuyuki Yamada, Kentaro Tanaka, and Yutaka Majima
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Itinerant ferromagnetism and geometrically suppressed metal-insulator transition in epitaxial thin films of Ca2RuO4

Ludi Miao, Punam Silwal, Xiaolan Zhou, Ilan Stern, Jin Peng, Wenyong Zhang, Leonard Spinu, Zhiqiang Mao, and Dae Ho Kim

Appl. Phys. Lett. 100, 052401 (2012); http://dx.doi.org/10.1063/1.3680250 (3 pages) | Cited 1 time

Online Publication Date: 31 January 2012

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We have investigated the effect of epitaxial strain on the electrical and magnetic properties of high quality Ca2RuO4 films on LaAlO3 (001) substrates. The films exhibit low temperature itinerant ferromagnetic ground state and significantly suppressed metal-insulator transition due to epitaxial strain. An anomaly in the in-plane resistivity was also observed near the Néel temperature. Symmetry analysis of anisotropic magnetoresistance suggests a phase coexistence of ferromagnetic metal and antiferromagnetic insulator in ground state.
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73.61.Ng Insulators
75.50.Dd Nonmetallic ferromagnetic materials
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.30.+h Metal-insulator transitions and other electronic transitions
75.70.Ak Magnetic properties of monolayers and thin films

Fabrication and magnetic properties of free-standing Ni nanotube arrays with controllable wall thickness

Y. L. Li, S. L. Tang, R. Xie, Y. Wang, M. Yang, J. L. Gao, W. B. Xia, and Y. W. Du

Appl. Phys. Lett. 100, 052402 (2012); http://dx.doi.org/10.1063/1.3681136 (3 pages) | Cited 2 times

Online Publication Date: 31 January 2012

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Free-standing Ni nanotubes were fabricated on silicon substrate using anodic aluminum oxide/polypyrrole composite template. The diameter, length, and wall thickness of the nanotubes can be precisely and independently controlled. Magnetic measurements show that the magnetic anisotropic properties are strongly dependent on the wall thickness of nanotubes. Theoretical analysis and micromagnetic simulation were performed to explain the wall thickness-dependent anisotropic behavior.
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75.75.Cd Fabrication of magnetic nanostructures
75.30.Gw Magnetic anisotropy
75.50.Cc Other ferromagnetic metals and alloys
81.07.De Nanotubes

Influence of a transverse static magnetic field on the magnetic hyperthermia properties and high-frequency hysteresis loops of ferromagnetic FeCo nanoparticles

B. Mehdaoui, J. Carrey, M. Stadler, A. Cornejo, C. Nayral, F. Delpech, B. Chaudret, and M. Respaud

Appl. Phys. Lett. 100, 052403 (2012); http://dx.doi.org/10.1063/1.3681361 (3 pages) | Cited 9 times

Online Publication Date: 1 February 2012

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The influence of a transverse static magnetic field on the magnetic hyperthermia properties is studied on a system of large-losses ferromagnetic FeCo nanoparticles. The simultaneous measurement of the high-frequency hysteresis loops and of the temperature rise provides an interesting insight into the losses and heating mechanisms. A static magnetic field of only 40 mT is enough to cancel the heating properties of the nanoparticles, a result reproduced using numerical simulations of hysteresis loops. These results cast doubt on the possibility to perform someday magnetic hyperthermia inside a magnetic resonance imaging setup.
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87.19.Pp Biothermics and thermal processes in biology
87.61.-c Magnetic resonance imaging
75.75.-c Magnetic properties of nanostructures
72.30.+q High-frequency effects; plasma effects
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetostructural phase transitions and magnetocaloric effects in MnNiGe1−xAlx

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

Appl. Phys. Lett. 100, 052404 (2012); http://dx.doi.org/10.1063/1.3681798 (3 pages) | Cited 4 times

Online Publication Date: 1 February 2012

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The thermomagnetic and magnetocaloric properties of the MnNiGe1−xAlx system have been investigated by magnetization and differential scanning calorimetry (DSC) measurements. The presence of first-order magnetostructural transitions (MSTs) from hexagonal ferromagnetic to orthorhombic antiferromagnetic phases has been detected for x = 0.085 and 0.09 at 193 K and 186 K, respectively. The values of latent heat (L = 6.6 J/g) and corresponding total entropy changes (ΔST = 35 J/kg K) have been evaluated for the MST (x = 0.09) from DSC measurements. The magnetic entropy change for x = 0.09 (ΔSM = 17.6 J/kg K for 5 T) was found to be comparable with well-known giant magnetocaloric materials, such as Gd5Si2Ge2, MnFeP0.45As0.55, and Ni50Mn37Sn13.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Sg Magnetocaloric effect, magnetic cooling
64.70.kd Metals and alloys
72.15.Jf Thermoelectric and thermomagnetic effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
65.40.gd Entropy

All-metallic lateral spin valves using Co2Fe(Ge0.5Ga0.5) Heusler alloy with a large spin signal

Y. K. Takahashi, S. Kasai, S. Hirayama, S. Mitani, and K. Hono

Appl. Phys. Lett. 100, 052405 (2012); http://dx.doi.org/10.1063/1.3681804 (4 pages) | Cited 4 times

Online Publication Date: 1 February 2012

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A large spin signal (ΔRs) of 12.8 mΩ at room temperature is demonstrated in an all-metallic lateral spin valve (LSV) device comprising of ferromagnetic wire of a highly spin-polarized Co2Fe(Ge0.5Ga0.5) Heusler alloy and a Cu wire. From the results on multi-terminal LSV devices, the origin of the large ΔRs was concluded to be the high spin polarization of Co2Fe(Ge0.5Ga0.5) and the resultant small spin absorption. The all-metallic LSV device without MgO barrier has low contact resistance, which is considered to be beneficial for a high frequency ultrathin read sensor for the next generation ultrahigh density magnetic recording.
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75.47.Np Metals and alloys
73.40.Cg Contact resistance, contact potential

Dipolar ordering of random two-dimensional spin ensemble

Andrey V. Panov

Appl. Phys. Lett. 100, 052406 (2012); http://dx.doi.org/10.1063/1.3681788 (3 pages) | Cited 1 time

Online Publication Date: 2 February 2012

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We theoretically study the randomly positioned two-dimensional system of interacting magnetic dipoles representing the monolayer arrays of single-domain particles. It is showed the onset of the dipolar in-plane superferromagnetic ordering of Ising spins at the surface concentrations of nanoparticles above 0.24. The critical concentration of particles with random easy axis arrangement at zero temperature is 0.65. It is demonstrated that the ensemble with Ising arrangement of spins is ordered at high temperatures close to a particle Curie point.
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75.10.Hk Classical spin models
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ch Domain walls and domain structure
75.75.Fk Domain structures in nanoparticles

Anisotropy and extremely high coercivity in weak ferromagnetic LuFeO3

Wenka Zhu, Li Pi, Shun Tan, and Yuheng Zhang

Appl. Phys. Lett. 100, 052407 (2012); http://dx.doi.org/10.1063/1.3681789 (4 pages) | Cited 1 time

Online Publication Date: 2 February 2012

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The temperature dependence of the structural anisotropy of weak ferromagnetic LuFeO3 is investigated through the XRD spectra at different temperatures. The structural anisotropy decreases with heating, which is in agreement with the magnetization-temperature measurement. The magnetic hysteresis loops reveal exceptionally high coercivity and saturation field. Its high energy of magnetocrystalline anisotropy may be responsible for the peculiar phenomenon. Thus, LuFeO3 is a super hard magnetic material. The magnetized LuFeO3 can steadily provide weak permanent magnetic field, which can be considered as a kind of useful application.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Gw Magnetic anisotropy
75.50.Vv High coercivity materials

Anisotropic magnetoresistance and weak spin-orbital coupling in doped ZnO thin films

Yufeng Tian, Weinan Lin, and Tom Wu

Appl. Phys. Lett. 100, 052408 (2012); http://dx.doi.org/10.1063/1.3681795 (3 pages) | Cited 5 times

Online Publication Date: 3 February 2012

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Both out-of-plane and in-plane anisotropic magnetoresistance (AMR) of Cu-doped ZnO thin films with different crystalline orientations are studied. Comparative data of angular dependent AMR suggest that the out-of-plane AMR comes from the geometric effect, while the in-plane AMR can be attributed to the field-dependent path-length effect. Moreover, the small magnitude of AMR and the negligible magnetocrystalline anisotropy suggest that the spin-orbit coupling in Cu-doped ZnO is relatively weak.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.30.Gw Magnetic anisotropy
68.55.J- Morphology of films

Improvement of coercivity and thermal stability of anisotropic Nd13Fe79.4B7Nb0.3Ga0.3 powders by diffusion of Pr-Cu alloys

Zhong Lin, Jingzhi Han, Meiying Xing, Shunquan Liu, Rui Wu, Changsheng Wang, Yan Zhang, Yingchang Yang, and Jinbo Yang

Appl. Phys. Lett. 100, 052409 (2012); http://dx.doi.org/10.1063/1.3681803 (4 pages) | Cited 3 times

Online Publication Date: 3 February 2012

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Highly anisotropic Nd13Fe79.4B7Nb0.3Ga0.3 powders from a self-organized rod-like disproportionation microstructure and room temperature magnetic properties of μ0Mr = 1.4 T, iHc = 13 kOe, and (BH)max = 41 MGOe are obtained by optimizing hydrogenation disproportionation desorption recombination (HDDR) process. Diffusion of Pr68Cu32 alloy into the HDDR powders further increases the coercivity of the powders to 18 kOe. This enhancement in coercivity is mainly attributed to the modification of grain boundaries including the decrease of Fe content and the increase of boundary thickness. The modified boundaries can work as effective pinning layers for domain walls. The thermal stability of magnetic properties of HDDR powders is also improved after the diffusion treatment.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ch Domain walls and domain structure
61.72.Mm Grain and twin boundaries

Multiferroic phase competitions in perovskite manganite thin films

M. H. Qin, Y. M. Tao, M. Zeng, X. S. Gao, S. J. Wu, S. Dong, and J.-M. Liu

Appl. Phys. Lett. 100, 052410 (2012); http://dx.doi.org/10.1063/1.3682079 (4 pages) | Cited 1 time

Online Publication Date: 3 February 2012

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Based on the Mochizuki-Furukawa model, the cycloidal spin structures of orthorhombic RMnO3 manganite thin films on various magnetic substrates are simulated using Monte Carlo method. It is revealed that the long range cycloidal spin order can be modulated by the film thickness and substrate spin structure. In particular, the ferromagnetic and antiferromagnetic spin orders of the substrate in different orientations have different pinning effects on the cycloidal spin order of the thin film. The simulated results are discussed in terms of the competition between the single-ion anisotropy and spin-orbit coupling.
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75.85.+t Magnetoelectric effects, multiferroics
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
77.80.Dj Domain structure; hysteresis
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.Nv Multiferroic/magnetoelectric films

Tuning the interlayer exchange coupling between single perpendicularly magnetized CoFeB layers

R. Lavrijsen, A. Fernández-Pacheco, D. Petit, R. Mansell, J. H. Lee, and R. P. Cowburn

Appl. Phys. Lett. 100, 052411 (2012); http://dx.doi.org/10.1063/1.3682103 (5 pages) | Cited 3 times

Online Publication Date: 3 February 2012

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We experimentally study the tunability of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interlayer exchange coupling (IEC) in Pt/CoFeB/Pt/Ru/Pt/CoFeB/Pt stacks with perpendicular magnetic anisotropy (PMA). The perpendicular magnetization of a single Pt/Co60Fe20B20/Pt (at. %) shows full remanence and square hysteresis loops for a CoFeB thickness range of 0.60–1.0 nm. By inserting a Pt layer between the Ru and CoFeB, the PMA of the ultrathin CoFeB layers is stabilized and the IEC can be tuned. In particular, we show that the IEC versus Pt thickness exhibits a simple exponential decay with a decay length of 0.16 nm.
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75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
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