We investigated possible candidates for a compensated half-metal (CHM) with a double perovskite structure A2CrRu(Os)O6 (A = Si, Ge, Sn, and Pb). Electronic structures and magnetic properties were analyzed using the accurate full-potential linear augmented plane wave method within the generalized gradient approximation (GGA). The compensated magnetism can be divided into half-metallic antiferromagnets (HM-AF) and antiferromagnetic insulator (AF-Is) based on their zero magnetic moments. A2CrRuO 6 (A = Si, Ge, Sn, and Pb) is a potential candidate for HM-AF, and Sn2CrOsO6 and Pb2CrOsO6 can be classified as AF-Is. The HM-AF and AF-Is states are both attributed to the superexchange and generalized double exchange mechanism. When the GGA + U calculation is taken into account, all A2CrRu(Os)O6 (A = Si, Ge, Sn, and Pb) states become unconventional AF-Is because the two AF state-coupled ions consisted of two different elements and the two spin-resolved densities of states were no longer the same. Further experimental confirmation will be done for the possible CHM of A2CrRuO6 (A = Si, Ge, Sn, and Pb), Sn2CrOsO6, and Pb2CrOsO 6.
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