Neutron diffraction studies of magnetic structure and phase transitions at very high pressures

High-intensity low-background neutron diffraction and high-pressure anvil technique have been used in the studies of magnetic materials up to the pressures of 10 GPa (sapphire anvils) and 24.5 GPa (diamond anvils) in the temperature range 1.5–300 K. Results of powder and single-crystal experiments are reported. A new magnetic state with partial moment reorientation has been detected in hematite α-Fe2O3, at pressures above 2.5–3 GPa. Incommensurate and commensurate phases in TbD2+x (x=0, 0.2), have been studied, stabilization of the incommensurate phase was found under pressure. The magnetic phase diagram of UAs has been determined, a sequence of magnetic structures (AF IA double-k, AF I double-k, AF I single-k) was observed at low temperatures when pressure was increased.