The Atoms Process, Microstruction And Magnetic Property Of FePt Based Nanocomposite Films

L1₀-FePt thin films have a magnetocrystalline anisotropy energy density Ku=5-10×10⁶J/m3, their superparamagnetic critical size is less than3nm, supporting recordingdensities of up to a Tbit/in2. As a result, L1₀-FePt thin films has been pursued as the mostpromised ultrahigh density magnetic recording. But, practical applications of FePt thinfilms face four scientific problems:1.decrease in media noise,2.reduction in orderingtemperature,3.mediation writing field,4.control of the FePt （001） texture.For solvingthese problems, it has great significance for promoting practical applications of FePt thinfilms.In this paper, the subjects about the atomic process of FePt/Ag nanocomposite filmsand microstructure and magnetic properties of FePt/TiNi nanocomposite films wasstudied by employing Vibrating Sample Magnetometer（VSM）, X ray-diffraction（XRD）,Transmission electron microscopy（TEM） techniques as following:By the ordering transition kinetic studies on the pressure of rate constants ofordering parameter variations, yielded by the growth activation volume and the phasetransition activation volume: the growth activation volume△V_g=（12.5±0.2） A³,about（0.91±0.01）Ω, the phase transition activation volum△V*=（13.9±0.3）A³,about（1±0.02）Ω, the analysis shows the growth of ordering domains and orderingtransition of FePt/Ag nanocomposite films is a thermal-vacancy-assisted process thatdepends on the diffusion of Ag atoms, in the ordering transition, Ag atoms is over500℃exudation temperature of FePt thin films, this explains Ag doping introduces vacancy andnot reduce the ordering temperature.Microstructure and magnetic properties FePt/TiNi nanocomposite films was beenstudied. The analysis found TiNi doping can decrease the exchange coupling between andreduce the grain, it can reduce dramatically the media noise. TiNi doping change themechanisms of FePt thin films, it changes from pinning filed based to nucleation filed. Italso resulted the decrease of coercivity, TiNi doping can promote the FePt （001） texture.