DECOUPLING THE STRUCTURAL AND MAGNETIC PHASE-TRANSFORMATIONS IN MAGNETOOPTIC MNBI THIN-FILMS BY THE PARTIAL SUBSTITUTION OF CR FOR MN

The first-order nature of the magnetic phase transformation at 360 deg rees C and the presence of a-Bi;rich eutectic at 265 degrees C have in hibited the application of MnBi thin films for high density magneto-op tical data storage. It is suggested that partial substitution of Cr fo r Mn should both lower;the Curie temperature, T-c, and decouple the la ttice and magnetic transitions so as to allow reversible Curie point w riting. It is found experimentally that 10% substitution of Cr for Mn reduces the apparent T-c to similar to 250 degrees C while retaining a Kerr rotation angle greater than 1 degrees at 633 nm, as measured thr ough the silica glass substrate. Observations of increasing H-c with t emperature in both MnBi and (Mn,Cr)Bi thin films suggest that the low- temperature phase is ferrimagnetic. (C) 1998 American Institute of Phy sics.