MAGNETIC-PROPERTIES OF NOVEL RESIN-BONDED EXCHANGE-COUPLED RARE-EARTHMAGNETS

The magnetic properties of compaction-molded resin-bonded magnets whic h exhibit exchange spring behaviour have been measured. The starting c ompositions of the alloys were Nd4.5Fe73B18.5Co3Ga1 and Nd3.5Dy1Fe73B1 8.5Co3Ga1 and the preparation method consisted of melt-quenching follo wed by annealing for a short period. The magnets have remanent magneti sation approximately 70% of saturation magnetisation. The variation of the magnetic properties with temperature in the range 250-320 K has b een investigated and magnetic viscosity measurements have been made. T hese data are compared with those from a conventional resin-bonded NdF eB-type permanent magnet. It has been found that the exchange coupled materials have smaller variations in magnetic properties over the temp erature range investigated, and they exhibit less time dependence of m agnetisation, compared with the conventional material.