Structure, Magnetic Properties, and Coercivity Mechanism of Rapidly Quenched MnxGa Ribbons

The microstructure, magnetic properties, and coercivity mechanism of rapidly quenched rare-earth-free L1₀-Mn_1.86Ga and D0₂₂-Mn₃Ga permanent magnetic ribbons have been investigated. The high remanence Mr of 61.3 emu/g and maximum energy product of 2.1 MGOe are obtained in L1₀-Mn_1.86Ga ribbons. The coercivity HC of L1₀-Mn_1.86Ga and D0₂₂-Mn₃Ga is 2.7 and 6.9 kOe, respectively. The different coercivity mechanisms and exchange coupling behavior have been discussed, upon the measurement of minor loops and Henkel plots. The minor second phase at grain boundaries in L1₀-Mn_1.86Ga ribbons may act as a pinning center of domain wall, thus reduce the exchange coupling. Both ribbons with Curie temperature >700 K may be promising permanent magnets at room temperature.