Muon Spin Relaxation and Magnetism in YMn_(2)D_(x) Deuterides

摘要

The interaction of hydrogen (deuterium) with Rare Earth compounds is a subject of considerable scientific and technological interest, as they readily absorb hydrogen, leading to substantial modifications of their physical properties. In the case of the YMn_(2) Laves phase compound, hydrogen changes the magnetization and distinctly increases the magnetic ordering temperature [1]. In contrast to pure YMn_(2) where magnetic ordering at 100K is accompanied by a huge lattice distortion, in the hydrides YMn_(2)H_(x) for x=1; 2; 3 the undistorted C15 type cubic structure is preserved below the ordering temperatures [2,3]. Muon spin rotation and relaxation (μSR) measurements made considerable progress in establishing the role of spin fluctuations in defining the magnetic and structural properties of YMn_(2) [4]. With the aim of a better understanding of the phenomena observed in hydrides, we performed the μSR experiments at the MuSR Facility of ISIS Rutheford Laboratory (GB). Zero and longitudinal field measurements were carried out in order to study magnetic behavior and spin fluctuations in YMn_(2)D_(1), YMn_(2)D_(2) and YMn_(2)D_(3) compounds over the temperature range 10-400K. The samples studied in these μSR measurements were prepared as deuterides in order to facilitate complementary neutron diffraction experiments on the same material. The YMn_(2) parent compound was fabricated from high purity materials in a standard induction furnace, and then deuterated in a constant volume apparatus. Measurements were made in longitudinal geometry in which the longitudinal relaxation function, G_(z)(t), is obtained by monitoring the time dependence of the muon decay asymmetry using detector arrays in the forward and backward directions.