Magnetic thin film research]: Progress report year 2

Abstract

The work in the past year has primarily involved four areas of magnetic thin films: amorphous rare earth-transition metal alloys, epitaxial CoPt{sub 3} and Ni-Pt alloy thin films, amorphous rare earth doped Si (a new class of dilute magnetic semiconductor with large negative magnetoresistance which the authors have discovered), and exchange-coupled antiferromagnetic insulators. In the amorphous alloys, they made a systematic study of the effects of local anisotropy, macroscopic (perpendicular) anisotropy, and exchange constant on the fundamental (and practical) properties of these magnetic alloys, as originally described in the grant proposal. The work on the epitaxial Co-Pt (and more recently Ni-Pt) alloys was originally undertaken as a comparison study to the amorphous alloys. Crystalline Co-Pt alloys have many striking similarities to the amorphous rare earth-transition metal alloys: perpendicular magnetic anisotropy, magneto-optic activity, and a {Tc} (for CoPt{sub 3}) somewhat above room temperature. They have discovered that these alloys exhibit a remarkable new phenomena; a surface-induced miscibility gap in a material which is believed to be completely miscible in the bulk. The authors are currently in several collaborations to measure specific heat of magnetic thin films. They used the specific heat to study antiferromagnetic superlattices, specifically NiO, CoO and MgO in various combinations to allow separation of effects of finite layer thickness and exchange coupling on the magnetic ordering.