MAGNETIC MATERIALS AND METHOD OF MAKING THEM

摘要

A method for the preparation of a two-phase magnetic material comprising as the major phase a crystalline alloy of one or more rare earth metals, boron and iron, substantially all of the crystallites of which have a size of less than 35 nanometres, and as the minor phase (alpha)-Fe, which method comprises the steps of (i) melt spinning an alloy consisting of up to 12 atomic percent of one or more rare earth metals, 3 to 7 atomic percent of boron and the balance iron or a mixture of iron and cobalt; (ii) quenching the melt spun alloy from step (i) under conditions such that a mixture of crystalline and amorphous material is produced, (iii) subjecting the material from step (ii) to an annealing treatment under conditions such that controlled crystal growth occurs to provide the crystalline alloy phase, substantially all of which has a particle size of less than 35 nanometres, the resulting materials having a remanence in excess of the theoretical value of 0.8 Tesla.