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Title: Finite size effects in L1{sub o}-FePt nanoparticles

Finite size effects on the temperature dependence of the uniaxial magnetic anisotropy, longitudinal and transverse susceptibilities and specific heat are examined for L1{sub o}-ordered FePt nanoparticles using an atomistic model based on an effective classical spin Hamiltonian. At low temperatures below criticality, we study the intrinsic uniaxial magnetic anisotropy energy (MAE) K{sub 1} and its scaling with magnetization K{sub 1}(T)∼M{sub s}(T){sup δ} and using Langevin dynamics simulations we show that the dependence of the exponent δ on the size L and aspect ratio of the grain arises from decomposition of the MAE into bulk and surface dependent terms. Monte Carlo simulations in the critical regime near the Curie temperature T{sub c}, show that the temperature variation of the specific heat and longitudinal susceptibility is given by finite size scaling relations c=L{sup α/ν}c{sup ~}(L{sup 1/ν}ϵ) and χ=L{sup γ/ν}χ{sup ~}(L{sup 1/ν}ϵ), respectively, where ϵ=(T−T{sub c})/T{sub c} is the reduced temperature, and the susceptibility scaling function χ{sup ~} can be approximated by a Lorentzian. Our estimates of the critical exponents α,γ, and ν appear to be in agreement with the universality class of the 3D Ising model.
Authors:
 [1] ; ;  [2]
  1. Department of Materials Science and Technology, P.O. BOX 2208, 71003 Heraklion (Greece)
  2. HGST, a Western Digital company, 3403 Yerba Buena Road, San Jose, California 95135 (United States)
Publication Date:
OSTI Identifier:
22266124
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 23; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANISOTROPY; ASPECT RATIO; COMPUTERIZED SIMULATION; CRITICALITY; CURIE POINT; DECOMPOSITION; HAMILTONIANS; ISING MODEL; MAGNETIZATION; MONTE CARLO METHOD; NANOSTRUCTURES; PARTICLES; SCALING; SPECIFIC HEAT; SPIN; TEMPERATURE DEPENDENCE