Magnetic properties, anisotropy parameters and magnetocaloric effect of flux grown MnFe4Si3 single crystal

Abstract

The transition-metal based alloy MnFe 4 Si 3 not only is a potential candidate for room temperature magnetocaloric applications, but also shows a large magnetic anisotropy forming an interesting case study in the search for rare-earth free permanent magnets. However, former polycrystalline and single crystal studies led to major disagreements about the order of the magnetic transition and the magnetocrystalline anisotropy scheme, which are two essential points for the understanding of this alloy. Here, magnetic, magnetocaloric properties and the magnetic anisotropy of MnFe 4 Si 3 (Mn~0 .86 Fe~4 .24 Si~2 .90) are investigated on a high quality single crystal grown by flux method, and compared to polycrystalline materials. Using the recently proposed criterion of field dependence of the magnetocaloric effect, we show that the ferromagnetic transition is more likely to be of second order, which is fully compatible with the absence of thermal hysteresis at the ferromagnetic transition in the present MnFe 4 Si 3 crystal. The c axis is confirmed to be the hard magnetic axis, both in single crystal and polycrystalline MnFe 4 Si 3 , and a large, dominant, K 1 anisotropy constant (~−2.5 MJ m −3) is found at low temperatures.