Evidence of unquenched Re orbital magnetic moment in $AA'FeReO_{6}$ double perovskites

Abstract

Spin and orbital magnetic moments of Re in AA'FeReO6 double perovskites (A,A' = Ba, Sr, Ca) have been directly probed employing XMCD spectroscopy at the Re L2,3-edges. A considerable orbital magnetic moment is observed in all the studied compounds despite octahedral coordination. Relative orbital to spin contribution per Re atom rises with lattice distortion from mL/mS = -0.28 to -0.34 for AA'=Ba2FeReO6 and Ca2FeReO6, respectively. A preliminary XMCD measurements at the Fe L2,3-edges reveals also a significant orbital moment of iron in Ca2FeReO6. The relation of the results to the magnetic properties of the compounds is discussed.