R&D: Influence of Finite-Size Effects on Curie Temperature of L10−FePt

Physical Review B has published an article written by Nguyen Thanh Binh, Sergiu Ruta, Department of Physics, The University of York, Heslington, York YO10 5DD, England, United Kingdom,Ondrej Hovorka, Faculty of Engineering and Physical Sciences, The University of Southampton, Southampton SO17 1BJ, England, United Kingdom,Richard F. L. Evans, and Roy W. Chantrell, Department of Physics, The University of York, Heslington, York YO10 5DD, England, United Kingdom.

Abstract: “We employ an atomistic model using a nearest-neighbor Heisenberg Hamiltonian exchange to study computationally the dependence of the Curie temperature of L10-FePt on finite-size and surface effects in heat-assisted magnetic recording (HAMR) media. We demonstrate the existence of a size threshold at 3.5 nm below which the impact of finite-size effects starts to permeate into the center of the grains and contributes to the reduction of the Curie temperature. We find a correlation between the Curie temperature and the percentage of atomistic bonds lost on the surface as a function of grain size, which can be extended to apply to not only L10-FePt but also generic magnetic systems of any crystal structure. In a recording medium, the inevitable grain size dispersion leads to an irreducible contribution to the dispersion of the Curie temperature. Therefore, our paper gives insight into finite-size effects, which have been predicted to be a serious limitation of HAMR.“