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P Bruno - One of the best experts on this subject based on the ideXlab platform.
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pressure dependence of the Curie Temperature in ni 2 mnsn heusler alloy a first principles study
Physical Review B, 2005Co-Authors: E şasioglu, L M Sandratskii, P BrunoAbstract:The pressure dependence of electronic structure, exchange interactions, and Curie Temperature in the ferromagnetic Heusler alloy ${\mathrm{Ni}}_{2}\mathrm{MnSn}$ has been studied theoretically within the framework of the density-functional theory. The calculation of the exchange parameters is based on the frozen-magnon approach. The Curie Temperature ${T}_{c}$ is calculated within the mean-field approximation by solving the matrix equation for a multisublattice system. In agrement with experiment the Curie Temperature increased from 362 K at ambient pressure to 396 K at 12 GPa. Extending the variation of the lattice parameter beyond the range studied experimentally, we obtained nonmonotonic pressure dependence of the Curie Temperature and metamagnetic transition. We relate the theoretical dependence of ${T}_{c}$ on the lattice constant to the corresponding dependence predicted by the empirical interaction curve. The Mn-Ni atomic interchange observed experimentally is simulated to study its influence on the Curie Temperature.
Daichi Chiba - One of the best experts on this subject based on the ideXlab platform.
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dependence of Curie Temperature on pt layer thickness in co pt system
Applied Physics Letters, 2015Co-Authors: Tomohiro Koyama, Aya Obinata, Yoshinori Hibino, A Hirohata, Balati Kuerbanjiang, V K Lazarov, Daichi ChibaAbstract:The Pt thickness dependence of the Curie Temperature of perpendicularly magnetized ultra-thin (Pt/)Co/Pt films has been investigated by magnetization measurements. The Curie Temperature and the saturation magnetic moment increase with the Co layer thickness and even with the Pt layer thickness. The Curie Temperature is found to have linear dependence on the total magnetic moment of the system and the coefficients of the linear fits are almost identical, regardless of whether the thicknesses of the ferromagnetic Co layer or the Pt layer are varied. The Curie Temperature also increases with the magnetic anisotropy, but no systematic dependence is observed. These results suggest that the magnetic moment induced in the Pt layer by the ferromagnetic proximity effect plays a significant role in determining the Curie Temperatures of such two-dimensional ferromagnetic systems.
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electrical control of Curie Temperature in cobalt using an ionic liquid film
Applied Physics Letters, 2012Co-Authors: Kazutoshi Shimamura, Daichi Chiba, Shimpei Ono, Shunsuke Fukami, Nobuyuki Ishiwata, Masashi Kawaguchi, Kensuke Kobayashi, Teruo OnoAbstract:The electric field effect on magnetization properties and Curie Temperature of Co ultra-thin films has been investigated. An electric field is applied to a Co film by using an electric double layer (EDL) formed in a polymer film containing an ionic liquid. The change in the Curie Temperature is ∼100 K by applying the gate voltage of ±2 V, suggesting that the observed large modifications of magnetization properties are attributed to the significant change in the Curie Temperature, which is induced by a large amount of carrier density control due to the formation of the EDL.
Koichi Niihara - One of the best experts on this subject based on the ideXlab platform.
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Curie Temperature Anomaly in Lead Zirconate Titanate/Silver Composites
Journal of the American Ceramic Society, 2005Co-Authors: Hae Jin Hwang, Toru Nagai, Tatsuki Ohji, Mutsuo Sando, Motohiro Toriyama, Koichi NiiharaAbstract:The Curie Temperatures of lead zirconate titanate-based (PZT-based) composites that were incorporated with silver particles were evaluated as a function of the silver content. Although the substitution of the silver ion has been considered to decrease the Curie Temperature, PZT/silver composites exhibited higher Curie Temperatures than those of monolithic PZT ceramics. It was found that the Curie Temperature gradually increased as the silver content increased. It was suggested that the observed Curie Temperature anomaly resulted from the relaxation of transformation-induced internal stress by intergranular silver particles.
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Curie Temperature anomaly in lead zirconate titanate silver composites
Journal of the American Ceramic Society, 2005Co-Authors: Hae Jin Hwang, Toru Nagai, Tatsuki Ohji, Mutsuo Sando, Motohiro Toriyama, Koichi NiiharaAbstract:The Curie Temperatures of lead zirconate titanate-based (PZT-based) composites that were incorporated with silver particles were evaluated as a function of the silver content. Although the substitution of the silver ion has been considered to decrease the Curie Temperature, PZT/silver composites exhibited higher Curie Temperatures than those of monolithic PZT ceramics. It was found that the Curie Temperature gradually increased as the silver content increased. It was suggested that the observed Curie Temperature anomaly resulted from the relaxation of transformation-induced internal stress by intergranular silver particles.
E şasioglu - One of the best experts on this subject based on the ideXlab platform.
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pressure dependence of the Curie Temperature in ni 2 mnsn heusler alloy a first principles study
Physical Review B, 2005Co-Authors: E şasioglu, L M Sandratskii, P BrunoAbstract:The pressure dependence of electronic structure, exchange interactions, and Curie Temperature in the ferromagnetic Heusler alloy ${\mathrm{Ni}}_{2}\mathrm{MnSn}$ has been studied theoretically within the framework of the density-functional theory. The calculation of the exchange parameters is based on the frozen-magnon approach. The Curie Temperature ${T}_{c}$ is calculated within the mean-field approximation by solving the matrix equation for a multisublattice system. In agrement with experiment the Curie Temperature increased from 362 K at ambient pressure to 396 K at 12 GPa. Extending the variation of the lattice parameter beyond the range studied experimentally, we obtained nonmonotonic pressure dependence of the Curie Temperature and metamagnetic transition. We relate the theoretical dependence of ${T}_{c}$ on the lattice constant to the corresponding dependence predicted by the empirical interaction curve. The Mn-Ni atomic interchange observed experimentally is simulated to study its influence on the Curie Temperature.
Barry Cushing Stipe - One of the best experts on this subject based on the ideXlab platform.
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Curie Temperature Distribution in FePt Granular Media
IEEE Transactions on Magnetics, 2015Co-Authors: Simone Pisana, Shikha Jain, James W. Reiner, O. Mosendz, Gregory Parker, Matteo Staffaroni, Olav Hellwig, Barry Cushing StipeAbstract:The Curie Temperature distribution is an important parameter affecting transition noise in heat-assisted magnetic recording. In this paper, we follow up on our recent report on a technique to evaluate the Curie Temperature distribution and provide modeling that validates the method as well as provides the experimental bounds for its validity. Thermal modeling is used to determine whether the technique is sensitive to extrinsic sources of grain Temperature variations, such as distributions in thermal boundary resistance. The technique is applied to a variety of FePt granular media films of varying alloy composition and chemical ordering, and we find the Curie Temperature distribution to depend primarily on grain ordering kinetics. We also present results of grain switching probability as a function of the applied magnetic field and find a non-trivial dependence on the alloy magnetization.
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measurement of the Curie Temperature distribution in fept granular magnetic media
Applied Physics Letters, 2014Co-Authors: Simone Pisana, Shikha Jain, James W. Reiner, Gregory Parker, Olav Hellwig, C C Poon, Barry Cushing StipeAbstract:Heat assisted magnetic recording (HAMR) has been recognized as a leading technology to increase the data storage density of hard disk drives. Dispersions in the properties of the grains comprising the magnetic medium can lead to grain-to-grain Curie Temperature variations, which drastically affect the jitter in the recorded magnetic transitions and limit the data storage density capabilities in HAMR. Here we present a method to measure the switching probability of an ensemble of exchange-decoupled grains with perpendicular anisotropy subject to nanosecond heating pulses. The short heat exposure time ensures that the grains switch by reaching the Curie Temperature rather than through thermal activation. The switching probability can be directly interpreted as representing the Curie Temperature distribution. The method is applied to two sets of samples to reveal the sensitivity of the Curie Temperature distribution to FePt HAMR media fabrication parameters. This technique is of importance to engineer suitab...
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Size dependence of the Curie Temperature of L1o-FePt nanoparticles
Journal of Applied Physics, 2012Co-Authors: Andreas Lyberatos, Dieter Weller, Gregory John Parker, Barry Cushing StipeAbstract:Monte Carlo simulations using the single histogram method are performed to study the effects of finite size and Cu doping on the Curie Temperature of a single FePt nanoparticle. An atomistic model is used with an effective classical spin Hamiltonian constructed on the basis of first-principles calculations for L1o FePt. The Curie Temperature, evaluated from the peak in the Temperature variation of the magnetic susceptibility, is consistent with the finite-size scaling relation Tc(L)=Tc(∞)(1−xoL−1/ν), where L is the in-plane grain size, xo is found to depend on the grain aspect ratio, and the critical exponent of the correlation length is ν=1.06±0.06. A theoretical relation is obtained for the Tc dispersion arising from a lognormal grain size distribution. Addition of Cu results in reduction of the Curie Temperature proportional to the dopant content.
