High coercivities in as-cast Nd-Fe and Nd-Fe-Ti alloys

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Abstract
Bulk Nd73Fe27 and Nd66.8Fe24.7Ti8.5 alloys exhibit relatively high coercivities with a room‐temperature value of about 5 kOe. The origin of the high coercivities has been investigated with magnetic and structural studies. Thermomagnetic data show the presence of a magnetic phase with a Curie temperature of about 270 °C which is close to that of NdFe2. This phase is metastable changing to a magnetic phase with an ordering temperature of 65 °C after heating to 700 °C. The lower Curie temperature phase is related to Nd2Fe17. The coercivity of the sample decreased to negligible values after the heat treatment. It is believed that the high coercivities are due either to the anisotropic NdFe2 phase or possibly to an oxygen‐stabilized Nd‐Fe‐O phase which is probably present in the form of fine particles.