High-Pressure Magnetic Properties Of Antiferromagnetic Samarium Up To 30 Gpa Using A Squid-Based Vibrating Coil Magnetometer

Samarium (Sm) has antiferromagnetic (AFM) ordering at the hexagonal site at T-N(hex) = 106 K, and at the cubic site at T-N(cub) = 14 K at ambient pressure. The structural transition from the so-called Sm-type structure to the double hexagonal close-packed (dhcp) structure occurs at approximately 6 GPa. According to electrical resistance measurements, the shift of T-N(hex) toward the low-temperature side occurs simultaneously with the shifting of T-N(cub) toward the high-temperature side with increasing pressure. We conducted dc magnetic measurements on Sm at high pressure up to 30 GPa using a SQUID-based vibrating-coil-magnetometer to pursue T-N(cub) at high pressure: The magnetic measurements revealed stepwise anomalies below 2 GPa. A ferromagnetic (FM) anomaly was observed in the dhcp structure, suggesting that spins at both structural sites formed the FM magnetization. In the face-centered cubic (fcc) structure at above 12 GPa, a reduction in the magnetic signal occurred. In the distorted fcc structure at above 20 GPa, sufficient suppression of the FM moment was observed and afterward the diamagnetic signal suggesting the possibility of superconductivity was observed.