Analyses of Knight shifts (K) in transition metals commonly assume that the s and d bands are distinguishable at the Fermi energy (i.e., small s-d hybridization). The three major contributions to K are attributed to unpaired s electrons (Ks), unpaired d spins (Kd) and orbital angular momentum (Korb) each arising from counterpart terms in the susceptibility, χ. This partitioning (valid for weak spin-orbit interactions) allows one to relate the s and d contributions to χ to the corresponding densities Ns(EF) and Nd(E F). One further assumes that Ns(E) varies much more slowly than Nd(E) so that the d-spin susceptibility is the only temperature-dependent term. The free-electron description is then used to calculate Ks. We report here investigations of contributions to Knight shifts (and relaxation rates) using ab initio SRAPW band calculations, the combined interpolation scheme and the QUAD scheme. Strong s-d hybridization is found to cause substantial structure in the projected Ns(E) for fcc Ni, Pd and Pt, as was found earlier for Fe. This structure can cause K s to be temperature dependent [if EF falls at a peak in Ns(E)] and can affect strongly the Van Vleck susceptibility and hence Korb. The structure effect is found to be very weak in the metals mentioned but preliminary results for hcp Sc (and possibly Gd) and bcc Cr and V indicate that larger effects may be expected.
ASJC Scopus subject areas
- Physics and Astronomy(all)