Relationship of magnetic ordering and crystal structure in the lanthanide ferromagnets Gd, Tb, Dy, and Ho at high pressures

The pressure dependence of the magnetic ordering temperatures for the lanthanide ferromagnets Gd, Tb, Dy, and Ho has been investigated in the pressure region up to 18 GPa by two types of magnetic measurements using a superconducting quantum interference device (SQUID). The present magnetic measurements enabled us to investigate the pressure dependence of the magnetization intensity at low magnetic fields as well as the magnetic ordering temperatures. Their results are interpreted in the light of such previous experiments as magnetic susceptibility, magnetization, electrical resistance, neutron diffraction, and M\ossbauer spectroscopy measurements. All of the magnetic orderings in the above four elements were suppressed down to less than the detection level, being related to the structural transition. The ferromagnetic ordering in Gd, Tb, Dy, and Ho is stabilized in the hcp structure. The magnetic anomalies due to the helimagnetic ordering of Tb and Dy disappear at the Sm-to-dhcp transition and the hcp-to-Sm transition, respectively, while that of Ho disappears in the Sm-type phase near the Sm-to-dhcp transition.