Microstructure and magnetic properties of nanocomposite FePtCr–SiN thin films

Abstract

͓͑FePt͒ 100Ϫx Cr x ͔ 100-␦ -͓SiN͔ ␦ nanocomposite thin films with xϭ0 -25 at. %, and ␦ ϭ0 -30 vol. % were fabricated on a natural-oxidized Si͑100͒ substrate by dc and rf magnetron cosputtering of FePt, Cr, and Si 3 N 4 targets. The thickness of the films was kept at 10 nm in order to examine the possibility for applying in high-density magnetic recording media. Transmission electron microscopy ͑TEM͒ and electron diffraction analyses indicated that the face-centered-cubic ͑fcc͒ ␥-phase FePt, body-centered-cubic ͑bcc͒ Cr, and amorphous SiN coexisted in as-deposited films. The as-deposited films were annealed in vacuum between 350 and 750°C for 30 min, and then ice-water quench cooling, in order to transform the soft magnetic fcc ␥-FePt phase to the hard magnetic face-centered-tetragonal ͑fct͒ ␥ 1 phase. Cr was added to inhibit the FePt grain growth, and was observed by TEM and energy disperse spectrum analysis in the grain surface area of FePt grains. The TEM observation indicated that the structure of the film was an amorphous SiN matrix with FePtCr particles dispersed in it. The particle size of FePtCr in annealed film was increased with the annealing temperature but decreased with the increase of SiN and Cr contents. Magnetization measurements indicated that the optimum condition for high-density magnetic recording purpose of the film was found with xϭ10 at. % and ␦ϭ15 vol. %, annealing at 600°C for 30 min. The average grain size of the FePtCr in this film is about 9.5 nm, the saturation magnetization is 450 emu/cm 3 , in-plane coercivity is 3.7 kOe, and in-plane squareness is about 0.75.

Microstructure and magnetic properties of Ag/FePt double layer films with different cooling processes

“…FePt thin films with the L1 0 structure have been intensively investigated in recent years due to its high magnetocrystalline anisotropy (Ku ∼7 × 10 7 erg/cm 3 , H k ∼100 kOe), therefore, it is a potential candidate for ultrahigh-density magnetic recording. However, the formation of L1 0 -FePt film requires a heat treatment at a high temperature around 600 • C, which results in the grain growth [5,6]. Some investigations in lowering the ordering temperature and enhancing the coercivity of FePt film have been reported, such as doping a third element [7,8,9] and introducing an underlayer [10,11,12] and a capped layer [13] to the FePt film.…”

Granular $\hbox{Co}_{3}\hbox{Pt}$ Thin Films With Perpendicular Hard Magnetic Properties for Perpendicular Magnetic Recording Media

“…Therefore, materials with high value are generally attractive for ultra high density magnetic recording applications because they allow smaller grains to keep thermal stability. Although of FePt is as high as erg/cm , the ordering temperature of FePt films is usually higher than 500 C [2], [3], which results in the particles agglomerate and grain growth. On the other hand, of hcp Co Pt alloy film is also as high as erg/cm , and the temperature for obtaining high perpendicular magnetic properties is consistent with the current manufacture temperature of hard disc [4].…”

Microstructure and magnetic properties of FePt-SiO2 granular films with Ag addition

“…Many investigations on the fabrication of the FePt granular films by the sputtering technique have been made. [22][23][24][25][26][27][28] However, controlling the particle size is difficult since most of the granular films are deposited at room temperature, and a postannealing becomes necessary for the L1 0 ordering. Okamoto et al fabricated FePt-AlN and FePt-MgO granular films on heated MgO substrates; 22 however, the average particle size was too large to be considered for the high-density recording media.…”