Hyperfine fields at the Fe sites in FeX (X: Hf, Mo, Nb, Ta, Ti, V, Zr) intermetallics.

FERNANDEZ, VICTORIA; GIL REBAZA, ARLES; ELENO, LUIZ; PETRILLI, HELENA; SCHÖN, CLAUDIO; ERRICO, LEONARDO

Canberra

Conferencia; Joint International Conference on Hyperfine Interactions and Symposium on Nuclear Quadrupole Interactions 2014; 2014

Australian National University

Electronic structure calculations based on density functional theory (DFT) with the local spin density approximation (LSDA) or the semi local (generalized gradient approximation, GGA) for the exchange and correlation potential has been shown to be very successful for the prediction and understanding of different structural, electronic, and magnetic properties of solids. However, the exchange and correlation effects included in the LSDA and GGA approximations are insufficient in most cases and several shortcomings are known to appear when these approximations are applied to magnetic systems. One of them is the (severe) underestimation of the hyperfine field, Bc, on the nuclei site of 3d metal atoms.In the past years, several attempts had been made in order to calculate the contact hyperfine fields at the nucleus of 3d metals. In particular, P. Novak and V. Chlan [1] used the fact that the magnetic moments of 3d atoms predicted by ab initio calculations are in much better agreement with the experiments than Bc to propose a semi empirical correction to the contact field at Fe sites in different iron compounds. The authors found that the core and valence contributions to Bc are proportional to the magnetic moments of the 3d (μd) and 4s (μs) electrons of Fe, respectively, so that the contact hyperfine field can be written as their linear combination. The coefficients of the linear combination were adjusted by comparison with the hyperfine fields determined experimentally in a number of iron compounds. Using this semi empirical method an excellent agreement between theory experiment-experiment was found.In this work, based on the idea reported in [1], we study several FeX intermetallic alloys in the B2, B32 and D03 phases. In this way we extend the study to metallic systems whose magnetic moments are within the range of 1.0 to 2.0 μB. As in Ref. 1, a general linear correlation between μd and the core contribution to BC is obtain, but the slope of this correlation is different from that found by Novak and Chlain in semiconductors. We also found that the valence contribution is proportional to μs but the correlation is not universal: the slope of the linear function is different for each FeX-phase. The dependence of the correlation on the parameterization employed for GGA is also discussed.