Electronic origin of ferroic quadrupole moment under antiferroic quadrupole orders and finite magnetic moment in $J_{\rm eff}=3/2$ systems

Abstract

We study the electronic origin of parasitic ferroic quadrupole moments in antiferroic quadrupole orders by extending a model studied in G. Chen et al., Phys. Rev. B 82, 174440 (2010) with the effective angular momentum $J_{\rm eff}=3/2$ quartet ground states. Taking into account the first crystalline-electric-field (CEF) excited doublet, cubic anisotropy in the quadrupole moments emerges, which leads to the induced ferroic quadrupole moments in the antiferro quadrupolar phases. The hybridization with the CEF excited quartet states also causes finite magnetic moments compatible to the observed size of the effective moment in typical $J_{\rm eff}=3/2$ systems, as opposed to the naive expectation of vanishing moments in the $J_{\rm eff}=3/2$ systems. These results suggest the importance of the corrections arising from the high-energy CEF excited states in the $J_{\rm eff}=3/2$ systems.