REMARKABLE IMPROVEMENT OF THE COERCIVITY OF TbMn₆Sn₆ COMPOUND BY MELT-SPINNING PROCESS

The melt-spinning process has been carried out to improve the hard-magnetic properties of the TbMn₆Sn₆ compound. For the TbMn₆Sn₆ ribbons quenched at a rate of 40m/s and annealed at 545K for 30min, the highest coercivity of about 0.6T is achieved at room temperature, which is much higher than that of the TbMn₆Sn₆ ingot. Both the ingot and the ribbon coercivities will increase with decreasing temperature. For ribbons, a greater improvement of coercivity has been made at lower temperatures. Microstructural studies show the uniform nanocrystalline distribution in the TbMn₆Sn₆ ribbons and a small amount of Tb-rich phase in grain boundaries. The observed remarkable improvement of magnetic hardening in ribbons is believed to arise from the uniform nanoscale microstructure and the domain-wall pinning at the grain boundaries.