Orbital-ordering-induced metal-insulator transition in PrRu 4P12

Abstract

The metal-insulator (M-I) transition in PrRu4P12 results neither from magnetic ordering nor from pure local crystal distortion, since small local distortion failed to produce the insulating phase at low temperature. In this paper, we suggest that the M-I transition at TMI = 62.3 K might originate from the spontaneous orbital ordering of Pr 3+ f-electrons. The 'ferro-orbital' ordered state and the 'antiferro-orbitar ordered state correspond to the Im3 state above and the Pm3 state below the M-I transition. These orbital ordered states not only yield the right transport properties and correct crystal field states across the phase transition, but also can be checked by polarized synchrotron x-ray diffraction measurement. This study has been carried out within the framework of the ab initio local density approximation+U method. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.