Decoupling the structural and magnetic phase transformations in magneto-optic MnBi thin films by the partial substitution of Cr for Mn

Abstract

The first-order nature of the magnetic phase transformation at 360 °C and the presence of a Bi-rich eutectic at 265 °C have inhibited the application of MnBi thin films for high density magneto-optical data storage. It is suggested that partial substitution of Cr for Mn should both lower the Curie temperature, Tc, and decouple the lattice and magnetic transitions so as to allow reversible Curie point writing. It is found experimentally that 10% substitution of Cr for Mn reduces the apparent Tc to ∼250 °C while retaining a Kerr rotation angle greater than 1° at 633 nm, as measured through the silica glass substrate. Observations of increasing Hc with temperature in both MnBi and (Mn,Cr)Bi thin films suggest that the low-temperature phase is ferrimagnetic.