Hydrogen-induced reduction of electric field gradient in La 2Fe 14BH x studied by NMR on 139La

Abstract

The 139La NMR spin-echo spectra of La 2Fe 14BH x are reported. Since lanthanum has no 4f electrons, the observed quadrupole splittings are directly proportional to the lattice part of the electric field gradient, V zz lat. This quantity decreases as the content of interstitial hydrogen x grows. To describe the fall-off of V zz lat, a dimensionless function f 2( x) is introduced, normalised so that f 2(0)=1. Analysis of the new and earlier published data obtained by several experimental techniques demonstrates that the reduction of both the second-order crystal field parameter A 20 and the lattice electric field gradient V zz lat is described by the same function f 2( x) in all R 2Fe 14BH x . The only distinction that needs to be made is between R being a light and a heavy rare earth.