Hydrogen-induced reduction of electric field gradient in La2Fe14BHx studied by NMR on 139LA

The La-139 NMR spin-echo spectra of La2Fe14BHx 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 AN and the lattice electric field gradient V-zz(lat) is described by the same function f(2)(x) in all R2Fe14BHx. The only distinction that needs to be made is between R being a light and a heavy rare earth. (C) 2003 Elsevier Ltd. All rights reserved.