Spin Kinetics of Liquid 3He in Contact with a DyF3 Micropowder at Ferromagnetic Ordering of Dy3+ Ions

The spin kinetics of liquid 3 He in contact with a mixture of LaF 3 (99.67%) and DyF 3 (0.33%) micropowders at temperatures of 1.5–3 K has been studied by pulsed nuclear magnetic resonance (NMR). The DyF3 is a dipolar dielectric ferromagnet with the phase transition temperature T c = 2.55 K, whereas the diamagnetic fluoride LaF 3 is a diluting substance for the optimal observation conditions of 3 Не NMR in powder pores. The magnetic phase transition in DyF 3 is accompanied by a considerable change in the character of fluctuations of the magnetic moments of dysprosium ions, which affect the spin kinetics of 3 Не in contact with the substrate. Significant changes in the relaxations rates of the longitudinal and transverse magnetizations of 3Не have been discovered in the region of magnetic ordering of the solid matrix. The technique of studying the static and fluctuating magnetic fields of a solid matrix at low temperatures using liquid 3 He as a probe has been proposed.