CrPt3 thin film media for perpendicular or magneto-optical recording

The magnetic properties of CrPt3 L1(2) ferrimagnetic thin films have been studied. Films were produced by sputtering multilayers of Cr and Pt onto silicon nitride coated silicon substrates. The as-deposited films are nonmagnetic. An anneal at similar to 800 degrees C results in ferrimagnetic behavior with a perpendicular easy-axis. X-ray diffraction and transmission electron microscopy (TEM) measurements show that (111) CrPt3 is the only crystalline phase present after annealing. Rocking curves with a full width at half maximum as low as 1.8 degrees indicate good crystallographic orientation. Magnetic properties of the films vary with composition, annealing temperature and time, layer thickness, and sputtering conditions. The films exhibit large coercivities, H-c, that can be tuned in the range 1500-8000 Oe. Saturation magnetization, M-s, is typically 150-200 emu/cc. Squarenesses, S, as high as 0.99 have been found. A uniaxial magnetic anisotropy constant, K-u, of up to 8 X 10(6) erg/cc was achieved. TEM micrographs show a 35 nm average grain size and complete interdiffusion of the Cr and Pt. Magneto-optical hysteresis loops at 632.8 nm wavelength reveal Kerr rotations of about 0.21 degrees when the films are overcoated with a quarter-wavelength dielectric. (C) 1999 American Institute of Physics. [S0021-8979(99)50408-8].