Measurements of domain structure reformation temperatures in sintered Dy-free Nd2Fe14B magnets

Temperature dependences of remanences in imperfectly, partially, magnetized Dy-free Nd2Fe14B sintered magnets were measured. The domain structures in demagnetized and magnetized states were observed by Kerr effect microscopy and by magneto-force microscopy. The remanences in the samples after measurements of minor loops with applying of 0.1-1.6 T static and of 5 T pulse fields are mainly composed of the magnetized grains into single-domain state that are originally multi-domain grains in thermally demagnetized state. A specific temperature of about 500 K that corresponds to domain structure re-formation in the magnetized grains was detected in the measurements in this study