Low-temperature proton spin–lattice relaxation maxima of lanthanum hydrides doped with paramagnetic rare earth ions

Abstract

The low-temperature proton spin–lattice relaxation is analysed for lanthanum hydrides LaHx intentionally doped with Gd or Ce. These paramagnetic impurities were also characterized by static magnetic susceptibility and electron spin resonance measurements. A quantitative description of the proton relaxation rate maxima, as well as of the electron spin relaxation data, is presented. These analyses indicate that the density of states at the rare earth site disappears only for .

Nuclear spin-lattice relaxation in narrow gap semiconductors TiPtSn and ZrPtSn

“…We note, however, that the data deviate from the model fit below about 20 K. The low-T upturn in 1/T 1 indicates relaxation from extrinsic magnetic impurities (most likely) which, in some cases, can even cause the low-temperature relaxation maxima reported in Ref. [19].…”

Nuclear magnetic resonance studies of ball-milled hydrides

“…As explained in Refs. [18,19], the paramagnetic contribution to the spin-lattice relaxation rate can be expressed in the approximate form,…”

Metal-nonmetal transition of lanthanum hydrides, analyzed byLa139hyperfine interaction

“…Part of the samples were those used in earlier NMR studies. 3,14,26,28,29 The stoichiometry was analyzed twice and given to an error bar of ±0.015. For the NMR relaxation measurements, the powder samples were sealed in quartz ampoules of 6 mm diameter.…”

“…This has been substantiated for the same compound by magnetic characterization of Ce 3+ impurities before. 26 The observed T-dependent shift can be explained by the remnants of second order quadrupolar shift, Eq. ͑6͒, in spite of the magic angle spinning, because the linewidth increases in this temperature range ͓Fig.…”

“…However, using Gd 3+ 4f electron spin Korringa relaxation as a local conduction electron density probe, a decrease of the La-site specific density of states by at least a factor of 3 for 2.0ഛ x ഛ 2.87 was demonstrated recently. 12,26 Thus, the presently available experimental results concerning integral or site specific conduction electron density of state D͑E F ͒ must be assessed as contradictory.…”