Antiferromagnetic vs ferromagnetic interactions and spin-glass-like behavior in ruthenates

TL;DR

This study uses advanced density-functional calculations and neutron diffraction to explore magnetic interactions in Ca-substituted SrRuO3, revealing a transition from ferromagnetic to antiferromagnetic behavior and spin-glass characteristics.

Contribution

It provides a detailed magnetic phase diagram and highlights the importance of spin-orbit coupling in determining ruthenates' magnetic ground states.

Findings

Ca substitution reduces ferromagnetism and promotes G-type antiferromagnetism.

Spin-glass behavior with short-range antiferromagnetic interactions is observed in CaRuO3.

G-type antiferromagnetic state stabilizes around x=0.75 in Sr$_{1-x}$Ca$_x$RuO$_3$.

Abstract

We have made a series of gradient-corrected relativistic full-potential density-functional calculation for Ca-substituted and hole-doped SrRuO$_3$ in para, ferro, and $A$-, $C$-, and $G$-type antiferromagnetic states. Magnetic phase-diagram data for Sr$_{1-x}$Ca$_x$RuO$_3$ at 0 K are presented. Neutron diffraction measurement combined with total energy calculations show that spin-glass behavior with short-range antiferromagnetic interactions rules in CaRuO$_3$. The substitution of Sr by Ca in SrRuO$_3$ decreases the ferromagnetic interaction and enhances the $G$-type antiferromagnetic interaction; the $G$-AF state is found to stabilize around $x$ = 0.75 consistent with experimental observations. Inclusion of spin-orbit coupling is found to be important in order to arrive at the correct magnetic ground state in ruthenates.