Entangled origins of the nonmagnetic states of U and Fe atoms in hydrogenated UFeGe

The experimental ground state of hydrogenated UFeGe (H-UFeGe) is nonmagnetic (NM). This result is not expected since, first, both U and Fe atoms tend to be magnetic in their compounds and, second, the hydrogenation is considered as favorable for magnetism. There are two main scenarios to explain the observation of nonmagnetic U atoms in the U based materials: Pauli paramagnetism of the Stoner type and Kondo-type screening of the atomic 5f moments. We apply the local density approximation (LDA) and LDA+U methods to investigate the origin of the ground state of H-UFeGe. The LDA calculations give in agreement with experiment the NM state as the only self-consistent state. The absence of the magnetic moments of both U and Fe atoms is the result of the U 5f-Fe 3d hybridization. The LDA+U calculations with different U values reveal sensitive competition between NM and magnetic phases. The result of this competition depends nonmonotonously on the value of parameter U. We explain this nonmonotonous behavior by multiorbital nature of the 5f electron contributions to the electron structure of H-UFeGe combined with different responses of different orbitals to the correlation governed by U. Employing constraint calculations we demonstrate that in the magnetic phases the Fe atomic moments can be treated as induced by the U moments. Since the directions of the U and Fe spin moments are opposite, the mechanism of the induction is nontrivial. It includes the spin-projection-dependent charge redistribution and a peculiar influence of the spin polarization on the interatomic hybridization. We compare H-UFeGe with two other materials containing U and Fe atoms and establish important differences.

Automated summary

The experimental ground state of hydrogenated UFeGe is found to be nonmagnetic, which is unexpected considering the magnetic nature of U and Fe atoms. The LDA calculations reveal that the absence of magnetic moments in U and Fe atoms is due to the hybridization between U 5f and Fe 3d orbitals. Moreover, the competition between nonmagnetic and magnetic phases is observed in the LDA+U calculations.