KATO Takeshi NAGOYA UNIVERSITY, DEPT. ELECTRONICS, RESEARCH ASSOCIATE, 工学研究科, 助手 (50303665)
TSUNASHIMA Shigeru NAGOYA UNIVERSITY, DEPT. ELECTRONICS, PROFESSOR, 工学研究科, 教授 (80023323)
Magnetic anisotropy in MBE grown Co/Pt superlattices were investigated. The films were epitaxially grown on MgO (100) and (111) substrates as MgO (100), //Ag, Co/Pt (100),  and MgO (111), //Ag, Co/Pt , respectively. The perpendicular anisotropy were strongly dependent on the film orientation. Structural analysis by RHEED revealed the existence of a large tensile strain in the Co plane of the (100) films. The (100) films exhibit larger negative volume anisotropy compared to the (111) films, which is explained by the magnetoelastic effect through the positive magnetostriction constant λィイD2100ィエD2 of fcc Co. The large magnetocrystalline anisotropy was found by the analysis of the anisotropy energy in the film plane. The (100) and (111) films showed in-plane anisotropy with four fold and six fold symmetry, respectively and their values were considerably enhanced with decreasing Co thickness in Co/Pt superlattices.
PtィイD250ィエD2CoィイD250ィエD2 alloy films have been grown by MBE method onto heated MgO (100) and (111) substrates. It is found that the film with CuPt type structure is grown onto (111) substrate at a temperature of 300゜. Whereas, the crystal structure of the films grown onto (111) substrate at 500゜ and onto (100) substrate at 300゜ and 400゜ becomes PtCo ordered phase with AuCu structure. The film of the CuPt type exhibits a very large perpendicular magnetic anisotropy of 1.0×10ィイD16ィエD1 J/mィイD13ィエD1, due to the layered structure along the film normal direction. The spectrum of Kerr rotation θィイD2kィエD2 of the film with CuPt structure is considerably different from that of AuCu structure, not exhibiting a maximum around 4.0 eV but takes a peak at 1.4 eV.