The Study Of The Structure And Magnetic Properties Of The CoPt-C Nanogranular Films

Based on the study of PtCo -C magnetic recording films,[Co26Pt74(8A)/C(xA)]80(x=0-14) and [Co(xA)/Pt(12A)/C(6A)]40(x=2-12) samples were deposited by DCmagnetron sputtering. The multilayers were annealed at the temperature ranging from600 C to 850 C in 10-5Pa for 1 to 2.5 hours to form the nanoparticles. The structureand magnetic properties of the samples before and after annealing were studied.Some conclusions were obtained after investigated the structure and magnetic properties of PtCo/C films. l.The structures of the filmsIn the as-deposited films, PtCo atomic agglomerates are segregated by nonmagnetic C. Every agglomerate is about 0.5um. One agglomerate is composed of a great deal of grains.The grain size is about 20nm. Fcc(111) and (200) textures of Pt3Co , fct(111) texture of PtCo have been observed. Fcc texture predominates.After annealing, the textures of the films change markedly, fct(111) texture of PtCo and fcc(200) texture of Pt3Co have been observed in the nanogranular films [Co26Pt74(8A)/C(xA)]80 (x=0-14) .Fct texture predominates. Grain size keeps about 20nm. 2. The magnetic properties of the filmsCoercivity (Hc) and remanence ratio (Mr/Ms) of the films are very low .The samples show soft magnetism.Easy-axis of the annealed nanogranular films [Co26Pt74(8A)/C(xA)]80(x=0-14) lies in plane. The magnetism changes with the conditions of the deposition and annealing. Several points were discussed as follows.i. Hc is greatly improved from several Oe to nine thousands Oe with the rise of annealing temprature, but Mr/Ms decreases, which mainly because fcc texture changes into fct texture. ii. Hc and Mr/Ms rise with the extension of time, which also because the fcctexture changes into fct texture.iii. Hc and Mr/Ms firstly increase, then decrease with the increasing of C thickness from OA to 14A. The highest Hc and Mr/Ms are obtained when C thickness is 10A. iv. Hc decreases with the increasing of film thickness from 600A to 1400A.But Mr/Ms changes little.v. The operating pressure affects the magnetism greatly. From a lot of experiments we find that 0.5 Pa is the best.