Transition from Pauli paramagnetism to Curie-Weiss behaviour in vanadium

TL;DR

This study combines advanced theoretical methods to explain the temperature-dependent magnetic behavior of vanadium, revealing the emergence of local magnetic moments and incommensurate correlations without phase transitions.

Contribution

It demonstrates how local spin correlations and Hund's coupling lead to Curie-Weiss behavior in vanadium, bridging experimental observations with theoretical modeling.

Findings

Curie-Weiss law emerges at higher temperatures

Local moments originate from t2g states due to Hund's coupling

Incommensurate magnetic correlations are identified

Abstract

We study electron correlations and their impact on magnetic properties of bcc vanadium by a combination of density functional and dynamical mean-field theory. The calculated uniform magnetic susceptibility {in bcc structure} is of Pauli type at low temperatures, while it obeys the Curie-Weiss law at higher temperatures. Thus, we qualitatively reproduce the experimental temperature dependence of magnetic susceptibility without introducing the martensitic phase transition. Our results for local spin-spin correlation function and local susceptibility reveal that the Curie-Weiss behavior appears due to partial formation of local magnetic moments, which originate from $t_{2g}$ states and occur due to local spin correlations caused by Hund's rule coupling. At the same time, the fermionic quasiparticles remain well-defined, while the formation of local moments is accompanied by a deviation from the Fermi-liquid behavior. In particular, the self-energy of the $t_{2g}$ states shows the non-analytic frequency dependence, which is a characteristic of the spin-freezing behavior, while the quasiparticle damping changes approximately linearly with temperature in the intermediate temperature range $200$--$700$~K. By analyzing the momentum dependence of static magnetic susceptibility, we find incommensurate magnetic correlations, which may provide a mechanism for unconventional superconductivity at low temperatures.