Study of the temperature dependence of coercivity in MnBi

Two set of polycrystalline MnBi bulk samples, as-annealed and compacted powders, with different grain size, were prepared through powder metallurgy. Coercivity mechanisms were investigated by Kronmuller plot analysis, evaluating alpha and N-eff parameters, which take into account the effect of microstructure. The temperature dependence of coercivity of the as-annealed sample (alpha = 0.31) is compatible with pinning-type mechanisms, while that of the compacted powders (alpha = 0.41) indicates nucleation-type processes. Irreversible effects of temperature dependence of coercivity have been investigated.