MnBi nanostructures: Size dependence of magnetostructural transition and matrix templating

摘要

Rapidly solidified Mn_xBi_((1-x)) (x=0.05 Mn5, x=0.10 Mn10) alloys form as NiAs-type low-temperature phase MnBi nanoparticles in a Bi matrix. Microstructural differences underlie diverse magnetic behavior: Mn5 has well-separated nanorods along the basal plane axial directions of Bi, while Mn10 consists of MnBi nanorods and submicron-sized MnBi grains. The Curie transition of Mn10 is T_c=630 K with a second-order thermodynamic character, while Mn5 nanorods exhibit a reduced and hysteretic T_C=520 K. Magnetic field annealing fosters (00n) alignment of the MnBi phase. Mn10 also shows alignment of the Bi matrix by a proposed templating mechanism.