Effects of spin–orbit coupling and exchange in BaRuO3

Abstract

The magnetic behaviour of BaRuO₃ is examined in the light of its crystal structure and of Mössbauer data. The absence of long-range magnetic order at low temperature can be explained by spin–orbit coupling effects which are important for Ru^IV ions; these effects give a non-magnetic ground state (J= 0) for each site when the exchange is neglected.

The exchange contribution between the excited states can be expressed in terms of isotropic coupling, starting from Anderson's Hamiltonian. If we assume that the interactions within the (Ru₃O₁₂)^12– entities are dominant, its form is given by: ℋ_ex=–J/2[graphic omitted]L_iL_j(1 +L_iL_j)(1 +S_iS_j).

A qualitative analysis shows that these two contributions play a major role particularly in the low temperature range where the model agrees well with the Mössbauer results and the susceptibility curve.