Abstract
The experiment shows that hydrogenated is antiferromagnetic for . With increasing Fe content, the Néel temperature decreases and tends to 0 K at . Further increase of results in the ferromagnetism of the system. This paper suggests an explanation why the material that, from its chemical composition, is intermediate between antiferromagnet and Pauli paramagnet turns in the hydrogenated form to the ferromagnetic state—a state that is very unusual for the U compounds with the given crystal lattice. Our theoretical study is based on density functional theory (DFT) and calculations. It begins with the calculation of and in their experimental lattices. Next, we show that for the lattice parameters of becomes magnetic. To understand deeper the dependence of the magnetic states on the lattice parameters, we model quantum phase transitions in both parent systems. We find that a drastic difference of the hybridization in the two systems leads to fundamentally different types of the magnetic states. has well-defined U atomic moments and can be mapped on the Heisenberg-type Hamiltonian of interacting U moments. In , strong hybridization leads to both the Pauli paramagnetism for the equilibrium lattice and the simultaneous appearance of comparable in value U and Fe spin moments for larger lattice parameters. The presence of the Fe moments is shown to be essential for the magnetism of , which imposes strong constraint on the magnetic structure of the U sublattice requesting it to be ferromagnetic. The established correlation between U and Fe spin moments is crucial for the explanation of the ferromagnetism of the hydrogenated .
1 More- Received 7 December 2021
- Revised 31 March 2022
- Accepted 1 April 2022
DOI:https://doi.org/10.1103/PhysRevB.105.134411
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