Structure, magnetism and magnetocalorics of Fe-rich (Mn,Fe)1.95P1-xSix melt-spun ribbons

Single phase Mn0.66Fe1.29P1-xSix (0 ≤ x ≤ 0.42) compounds were synthesized using the melt-spinning (rapid solidification) technique. All the compounds form in the Fe2P-type hexagonal structure, except a Co2P-type orthorhombic structure of the Si-free Mn0.66Fe1.29P compound. The compounds with 0.24 ≤ x ≤ 0.42 present a FM-PM phase transition, while the compounds with lower Si content show an AFM-PM phase transition. In the Mn0.66Fe1.29P1-xSix compounds, TC and ΔThys are not only Si content dependent, but also magnetic field dependent. By increasing the Si content from x = 0.24 to 0.42, TC increases from 195 to 451 K and ΔThys is strongly reduced from ∼61 to ∼1 K. TC increases and ΔThys decreases with increasing magnetic field, ΔTC/ΔB is about 4.4 K/T. Mn0.66Fe1.29P1-xSix compounds show large saturation magnetic moments with values up to 4.57 μB/f.u.. A large MCE with a small thermal hysteresis is obtained simultaneously in Fe-rich Mn0.66Fe1.29P1-xSix melt-spun ribbons.