Exchange bias behavior on permanent magnet Nd-Fe-B

In this study, Nd-Fe-B magnets with the type of N42 were employed to modify the microstructure and the magnetic properties. The Nd2Fe14B spherical grains were enveloped in a Nd rich grain boundary phase, and they produced unordinary heterostructures. The exchange bias behavior on the permanent magnet Nd-Fe-B was investigated at 5 K. The temperature dependence of magnetization measurement found spin-reorientation transition in the vicinity of temperatureT = 100 K. When temperature under 100 K, ferromagnetic property played a major role with frozen magnetic moment. The coercivity at 5 K was larger but the negative saturated magnetic moments was lower compared to that at room temperature. In the magnetic hysteresis (M-H) loops at 5 K to 50 K, the negative shift ofHand the positive shift ofMalong axis increased sharply with the temperature drops. The training effect was observed due to the existence of frozen spin moment. The exchange bias could be ascribed to minor loop effect and unidirectional anisotropy with spin-reorientation transition.