Diamagnetic d¹⁰ and d⁰ cations direct magnetic interactions in double perovskites

The main magnetic interaction in oxides is superexchange mediated by oxygen anions. Recently, it has been shown that diamagnetic d¹⁰ and d⁰ cations can play a role in extended superexchange interactions due to differences in orbital hybridization. Here we formulate simple rules for this d¹⁰/d⁰ effect in A₂B'B''O₆ double perovskite oxides. We have investigated magnetic interactions in cubic Mn²⁺ double perovskites Ba₂MnTeO₆ (d¹⁰ Te⁶⁺) and Ba₂MnWO₆ (d⁰ W⁶⁺). Our analysis reveals d¹⁰ cations on the B'' site promote strong J₁ interactions, while d⁰ cations promote J₂ interactions. This effect is general to 3d transition metal double perovskites. The d¹⁰/d⁰ effect can be used to tune magnetic interactions and ground states as we have previously shown for Sr₂CuTe_1-xW_xO₆, where the ground state can be tuned from magnetic order to a random singlet state.

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