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Title: Magnetic anisotropy of FePt nanoparticles: temperature-dependent free energy barrier for switching

Abstract

We report the calculation of free energy with constrained magnetization for $$\lo$$ FePt nanoparticles. We employ effective spin Hamiltonian model constructed on the basis of constrained density functional theory calculations for $$\lo$$ FePt. In this model the Fe spins (treated as classical spins in this work) are coupled "directly" and via induced Pt moments with both isotropic and anisotropic interactions. Interactions mediated by the Stoner enhanced Pt moment stabilize ferromagnetic order and lead to a pronounced coordination dependence and long-range interactions. The free energy of these nanoparticles, as a function of the temperature and the constrained magnetization $$F(T,M_z)$$, is calculated from the joint density of states $g(E,M)$, using the extended Wang-Landau algorithm. The free energy barrier for magnetization reorientation is found to depend fairly linearly on the temperature in the ferromagnetic phase and vanishes in the paramagnetic phase.

Authors:
 [1];  [1];  [2]
  1. ORNL
  2. Seagate Research
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Center for Nanophase Materials Sciences
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
930847
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 10th MMM/Intermag joint conference, Baltimore, MD, USA, 20070107, 20070111
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; IRON ALLOYS; PLATINUM ALLOYS; ANISOTROPY; FREE ENERGY; NANOSTRUCTURES; SPIN; TEMPERATURE DEPENDENCE; HAMILTONIANS; MAGNETIZATION; PHASE TRANSFORMATIONS

Citation Formats

Zhou, Chenggang, Schulthess, Thomas C, and Mryasov, Oleg N. Magnetic anisotropy of FePt nanoparticles: temperature-dependent free energy barrier for switching. United States: N. p., 2007. Web.
Zhou, Chenggang, Schulthess, Thomas C, & Mryasov, Oleg N. Magnetic anisotropy of FePt nanoparticles: temperature-dependent free energy barrier for switching. United States.
Zhou, Chenggang, Schulthess, Thomas C, and Mryasov, Oleg N. Mon . "Magnetic anisotropy of FePt nanoparticles: temperature-dependent free energy barrier for switching". United States. doi:.
@article{osti_930847,
title = {Magnetic anisotropy of FePt nanoparticles: temperature-dependent free energy barrier for switching},
author = {Zhou, Chenggang and Schulthess, Thomas C and Mryasov, Oleg N.},
abstractNote = {We report the calculation of free energy with constrained magnetization for $\lo$ FePt nanoparticles. We employ effective spin Hamiltonian model constructed on the basis of constrained density functional theory calculations for $\lo$ FePt. In this model the Fe spins (treated as classical spins in this work) are coupled "directly" and via induced Pt moments with both isotropic and anisotropic interactions. Interactions mediated by the Stoner enhanced Pt moment stabilize ferromagnetic order and lead to a pronounced coordination dependence and long-range interactions. The free energy of these nanoparticles, as a function of the temperature and the constrained magnetization $F(T,M_z)$, is calculated from the joint density of states $g(E,M)$, using the extended Wang-Landau algorithm. The free energy barrier for magnetization reorientation is found to depend fairly linearly on the temperature in the ferromagnetic phase and vanishes in the paramagnetic phase.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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