[EN] Novel microwires of composition MnBi were obtained by means of quenching and drawing technique having a metallic nucleus of 50 μm diameter. Phase distribution analysis showed a composite microstructure comprising extensive zones of the ferromagnetic hexagonal MnBi phase (of up to 12 μm), interspersed within a matrix of diamagnetic Bi and some inclusions of pure Mn varying between 1 and 2 μm in length. A coercive field in excess of 4000 Oe was measured. Coercivity mechanism is described in terms of nucleation of reverse domains, for which the interface MnBi/Bi largely determines the hard magnetic response of the composite microwire.

Project UNAM-PAPIIT IN103216. J. Zamora is grateful for the scholarship received from UNAM-PAPIIT IN103216 and CONACYT-Mexico. Special thanks are given to Adriana Tejeda, Omar Novelo and Josue Romero (IIM-UNAM) for their valuable technical assistance. The work has been Fig. 3. Temperature dependence for a) maximum magnetization and b) coercive field of the MnBi microwire. Fig. 4. Fitting of experimental data for Eq. (1) (R2 = 0.998). 42 I. Betancourt et al. / Scripta Materialia 153 (2018) 40–43 partly supported by the Regional Government of Madrid under Project S2013/MIT-1942850, NANOFRONTMAG-CM