We fabricated thin L10-FexPt100-x (x = 46-54 at.%) polycrystalline perpendicular films, and examined the x dependences of the first-and second-order uniaxial magnetic anisotropy, Ku1 and Ku2, in relation to variant formation. The values of Ku1 and Ku2 were estimated from magnetic torque curves at an applied field of 70 kOe obtained using anomalous Hall effect. Ku1 for films with thickness d of 10 nm showed a maximum at x=50 at.%, which was consistent with the behavior of the order parameter. Ku1 decreased markedly as x increased from 50 at.%, accompanied by an increase of Ku2. In-plane X-ray diffraction analysis revealed that the variant formation increased markedly as x increased, especially beyond x = 50 at.%. Moreover, the relative lattice strain evaluated using a Williamson-Hall plot increased remarkably. The significant reduction of Ku1, accompanied by the enhancement of Ku2 , was coincident with variant formation. Ku1 for films with d = 2 nm also showed a maximum at x = 50 at.%. However, the Ku1 ∼ x relation showed a good symmetry against Fe content variations from 50 at.%. No increase of Ku2 with increasing x was observed. It is likely that a large tensile stress in the initial film growth, caused by the lattice misfit between FePt and MgO underlayers, suppressed the variant formation in these very thin films.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering