Effect of annealing time on the exchange coupling interactions and microstruc-ture of nanocomposite Pr_7.5Dy₁Fe₇₁Co₁₅Nb₁B_4.5 ribbons

Xiaoqian Bao, Yi Qiao, Xuexu Gao, Maocai Zhang, Jie Zhu, and Shouzeng Zhou State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China

摘 要：The influence of annealing time on the magnetic properties and microstructure of nanocomposite Pr7.5Dy1Fe71Co15Nb1B4.5 ribbons was systematically investigated by the methods of vibrating sample magnetometer （VSM）, X-ray diffraction （XRD） and high resolution transmission electron microscopy （HRTEM）. Interaction domains derived from strong exchange coupling interactions be- tween hard and soft magnetic grains were imaged using magnetic force microscopy （MFM）. Maximum remanence, intrinsic coerciv- ity, and maximum energy product values were obtained in the ribbons annealed at 700°C for 15 min, which were composed of Pr2（Fe, Co）14B, α-（Fe, Co）, and slight Pr2（Fe, Co）17 phases. Although Jr, Hci, and （BH）max decreased gradually with further increase of an- nealing time, it is emphasized that comparatively high Jr and Hci and （BH）max were obtained in a wide annealing time period of 15 to 360 min. The shape of initial magnetization curves and hysteresis loops change as a function of annealing time, indicating different magnetization reversal routes, which can be fully explained by the corresponding microstructure.

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