Quadruple perovskite oxide LaCu_3Co_2Re_2O_(12): A ferrimagnetic half metal with nearly 100% B-site degree of order

摘要

An A- and B-site ordered quadruple perovskite oxide LaCu_3Co_2Re_2O_(12) was synthesized at 9 GPa and 1323 K. The compound possesses a Pn-3 space group, where both A and B sites are orderly occupied by different cations with a nearly 100% degree of order. Bond valence sum calculations and x-ray absorption spectroscopy confirm the charge distribution to be LaCu~(2+) ~3Co~(2+) _2Re~(5.5+) ~2O_(12). A ferrimagnetic phase transition is found to occur around 150 K due to the Cu~(2+)(↑)-Co~(2+)(↑)-Re~(5.5+)(↓) spin coupling found by x-ray magnetic circular dichroism at Cu-, Co-, and Re-L_(2,3) edges. The magnetoresistance effects as well as the first-principle calculations indicate the half-metallic nature for LaCu_3Co_2Re_2O_(12) with a wider energy gap at the up-spin channel and a conducting band at the down-spin channel.