Effective control of the magnetic anisotropy in ferromagnetic MnBi micro-islands

This work shows the possibility of tailoring the magnetic anisotropy direction in ferromagnetic LTP-MnBi thin films from out-of-plane to in-plane while also making possible for the first time the growth of quasihexagonal LTP-MnBi micro-islands. This has been managed with no need to apply any external magnetic field, but only by controlling the temperature growth. The rf sputtering of a Mn-Bi composite target produces highly crystalline < 002 > oriented micro-islands with a size distribution in the micrometer range (up to 80 um) for samples grown at 300-425 K and < 110 > oriented elongated threads at 475 K. The < 002 > oriented films show perpendicular magnetic anisotropy while the < 110 > oriented ones show in-plane anisotropy. High values of coercivity have been obtained, reaching maximum values of 16.0 and 19.3 kOe at 300 and 400 K, respectively, for these LTP-MnBi thin films. Micromagnetic simulations have shown a clear correlation between the microstructure and the resulting magnetic properties. The route presented here represents a first step towards the possible fabrication of MnBi thin film micromagnets with customized magnetic anisotropy direction based on the deposition temperature. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

By controlling the growth temperature instead of applying an external magnetic field, the magnetic anisotropy direction in LTP-MnBi thin films was tailored successfully, leading to the growth of quasi-hexagonal micro-islands for the first time. Films with different orientations exhibited distinct magnetic anisotropy properties, with relatively high coercivity values.