MnBi nanoparticles with perpendicular magnetic anisotropy

A ribbon of a Mn-Bi meta-stable phase was fabricated by melt-spinning a Bi-rich Mn-Bi alloy (Mn10Bi90). Employing magnetic field heating to an as-spun sample up to 530 K in a magnetic field of 10 kOe results in a highly c-axis preferred orientation, showing the remanence magnetization ratio Mr/Ms ≈ 1.0 on the demagnetization curve for the heat-treated sample. The magnetic field heating also produces the c-axis preferred orientation in an ex situ annealed sample composed of MnBi particles with a random c-axis orientation. Investigating magnetization change upon changing the heating temperature suggests that MnBi particle rotation at an optimized heating temperature plays an important role in aligning the c-axis along the applied field.