MAGNETIC AND MAGNETOOPTICAL PROPERTIES OF AMORPHOUS RARE-EARTH-TRANSITION-METAL ALLOYS CONTAINING PR, ND, FE, CO

Amorphous rare-earth-transition-metal alloys of composition RE1-xFex and RE1-xCox with RE=Pr, Nd and 0<x<1 were prepared by coevaporation. Also disks for magneto-optical recording were fabricated using TbNd-FeCo or TbPr-FeCo layers. The magnetization, Curie temperature, uniaxial anisotropy, coercivity, and Faraday and Kerr rotation were investigated as a function of composition and temperature. The spectral variation of the Kerr rotation was measured for some alloys. The magnetization data indicate a strong dispersion of the Pr and Nd subnetworks and of the Fe subnetwork for Fe-rich alloys. The latter gives rise to a maximum of the Curie temperature T(C) around x=0.7 and to very low T(C) values for Fe-based alloys with x>0.9. The magneto-optical effects result from both the light rare earths and the transition-metal alloys giving rise to significantly larger rotations in-the visible as compared to the alloys containing heavy rare earths. Recording experiments on standard disks with a TbNd-FeCo layer indeed reveal good write/erase and read performances. The carrier-to-noise ratio ranges between 49 and 56 dB for wavelengths between 458 and 820 nm. Disks based on RE-TM layers containing Pr reveal a lower write/read performance and appear less suitable for magneto-optical recording.