Magnetic Properties of the Nanocrystalline Nd-Ho-Fe-Co-B Alloy at Low Temperatures: The Influence of Time and Annealing

摘要

A study is made of the effects of various factors such as time (7 years), temperature, high magnetic field up to 580 kOe and heat treatment (HT) on the morphological structure and magnetic hysteresis properties of a high-coercive nanocrystalline (Nd0.55Ho0.45)(2.7)(Fe0.8Co0.2)(14)B-1.2 alloy with a low temperature coefficient of remanence. We find a rather weak time effect on (Nd0.55Ho0.45)(2.7)(Fe0.8Co0.2)(14)B-1.2. After 7 years, the loss in the maximum magnetic energy product (BH)(max) is no more than 5%. Annealing of the sample at 250 A degrees C for 30 min decreases the amount of amorphous phase from 7.2 to 1.7%, while the grains' size of the 2-14-1 phase increases from 83 to 109 nm. For the HT alloy, a magnetization jump is observed at H similar to 500 kOe. It can be attributed to the first-order magnetization process or a spin-flip magnetic transition. Rectangularity of the hysteresis loop degrades after annealing. In case of the short-time heat treatment, losses in (BH)(max) are similar to 10%.