Competition of orbital, charge and spin degrees of freedom in Jahn–Teller magnets

Jahn–Teller (JT) magnets are compounds based on Jahn–Teller 3d- and 4d-ions with the $t_{2g}^{n_1}e_g^{n_2}$ configurations in a highly symmetric surroundings and with a ground state orbital E-doublet which are characterized by competition of various electronic degrees of freedom and strong electron-lattice interaction. In this paper, we present a generalized model of effective charge triplets, which allows, within a unified approach and in the most general form, to take into account charge, spin, orbital and lattice degrees of freedom for so-called single-band JT-magnets such as rare-earth nickelates RNiO$_3$.