Direct evidence of the orbital contribution to the magnetic moment in   AA'FeReO6 double perovskites
  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. 
M. Sikora, D. Zajac, C. Kapusta, M. Borowiec, C. J. Oates, V.   Prochazka, D. Rybicki, J. M. De Teresa, C. Marquina, M. R. I...