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

We have made a series of gradient-corrected relativistic full-potential density-functional calculations for Ca-substituted and hole-doped SrRuO3 in para, ferro, and A-, C-, and G-type antiferromagnetic states. Magnetic phase-diagram data for Sr1−xCaxRuO3 at 0 K are presented. Neutron diffraction measurements combined with total energy calculations show that spin-glass behavior with short-range antiferromagnetic interactions rules in CaRuO3. The substitution of Sr by Ca in SrRuO3 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.