Magnetic properties of permanent magnet for cryogenic undulator of permanent Shanghai synchrotron radiation facility

Abstract

M-H and M-T curve at cryogenic (10-300 K) of domestic Nd2Fe14B (N50M) permanent magnet are tested by physical property measurement system (PPMS). Br-T and Hci-T figure under the cryogenic condition for N50M are obtained. The orientation degree and three-dimensional magnetization are also analyzed and researched under the cryogenic conditon. The results show that N50M has a strong spin reorientation effect(SRT) between 80 and 150 K, Br shows a peak between 120 and 130 K and Hci increases linearly with temperature decresing. At 130 K, Br increases 15.6% and Hci increases 220% compared with at room temperature (300 K), reaching 1.65 T and 3638 kA/m respectively. Between 150 and 300 K, with temperature declining, the macroscopic orientation degree uniformity and the external magnetic field uniformity of N50M are improved gradually. Between 80 and 235 K, the micro-external magnetic field uniformity shows a deterioration phenomenon. The experimental research also indicates that near 235 K the N50M perpendicular to orientation direction presents a “remanent magnetization jump” phenomenon. The experimental results provide a reference for the physical design of cryogenic undulator for Shanghai Synchrotron Radiation Facility II and other high-precision cryogenic permanent magnet instruments and equipment.