Exceptionally strong magnetism in 4d perovskites RTcO3 (R=Ca,Sr,Ba)

TL;DR

This study reveals that 4d perovskites RTcO3 exhibit exceptionally strong magnetism with high Neel temperatures, driven by enhanced superexchange interactions due to their electronic structure and structural properties.

Contribution

It provides a detailed theoretical analysis of the magnetic properties of 4d perovskites RTcO3, highlighting their strong superexchange interactions and high magnetic ordering temperatures.

Findings

Large superexchange coupling constants (26-35 meV).

Neel temperatures range from 750 to 1200 K.

Magnetic properties increase with larger R ionic radius.

Abstract

The evolution of the magnetic ordering temperature of the 4d3 perovskites RTcO3 (R=Ca,Sr,Ba) and its relation with its electronic and structural properties has been studied by means of hybrid density functional theory and Monte Carlo simulations. When compared to the most widely studied 3d perovskites the large spatial extent of the 4d shells and their relatively strong hybridization with oxygen weaken the tendency to form Jahn-Teller like orbital ordering. This strengthens the superexchange interaction. The resulting insulating G-type antiferromagnetic ground state is characterized by large superexchange coupling constants (26-35 meV) and Neel temperatures (750-1200 K). These monotonically increase as a function of the R ionic radius due to the progressive enhancement of the volume and the associated decrease of the cooperative rotation of the TcO6 octahedra.