Magnetism in α-RuCl₃: Dependence on Coulomb Interaction and Hund’s Coupling

Employing the density functional theory, we have investigated the roles of Coulomb and Hund’s interactions in the electronic and magnetic properties of newly discovered α-RuCl₃ having the R3 ¯ symmetry, which is in close proximity of the Kitaev system. We show that both the size and the direction of local magnetic moment are highly dependent on Coulomb and Hund’s interactions, and the spin and orbital parts show different behaviors. The validity of the so-called j^eff picture is accessed upon interaction parameters, and the explicit roles of Hund’s interaction in the local electronic structures and magnetic properties are discussed.