Evidence of exchange coupling in τ-MnAlC/FeCo system

Abstract

The τ-MnAlC/FeCo system has potential to be applied as rare earth-free permanent magnet, due to exchange coupled between hard and soft magnetic phases as alternative for the development of high energy product permanent magnets. In this work the hard-magnetic phase Mn53.3Al45C1.7 (μ0Hc = 0.37 T of coercive force, Mr = 23.52 Am2/kg of remanent magnetization, Ms = 52.94 Am2/kg of saturation magnetization and (BH)max = 3.89 kJ/m3 of maximum energy product) was mixed with the soft magnetic phase Fe65Co35 (μ0Hc = 0.007 T and Ms = 221.33 Am2/kg) using a solid-state procedure. The magnetic materials were sintered using different ratios of hard and soft magnetic phases: 95:5, 90:10, 85:15 and 80:20; and different sintering temperatures (300, 400, 500 and 600 °C) in order to improve the magnetic properties. The magnetic exchange coupling between MnAlC and FeCo was proved by the hysteresis loop and its corresponding Thamm-Hesse analysis. The best result was obtained for MnAlC/FeCo (95/5 wt%) sintered at 500 °C during 30 min, for which the magnetic properties were μ0Hc = 0.277 T, Ms = 76.43 Am2/kg and (BH)max = 5.57 kJ/m3.