Orientation of Nd and Mn magnetic moments in a CMR Nd0.72Ba0.28MnO3 by X-ray magnetic circular dichroism

X-ray absorption and X-ray magnetic circular dichroism at Mn L-2.3- and Nd M-4.5-edges of a twinned Nd0.72Ba0.28MnO3 single crystal have been performe d versus temperature (between 10 and 300 K) and applied magnetic field (bet ween 0 and 6.5 T). The results show that neodymium cations order below 70 K with the magnetic moments antiparallel to the manganese subnetwork in weak applied magnetic field (<1.5 T). For higher magnetic field, the neodymium moments turn parallel to the manganese ones showing that the antiferromagne tic exchange coupling between both subnetworks is weak. The presence of a m etal-insulator transition below 70 K in the studied single crystal correlat ed to the magnetic ordering of neodymium cations can be understood on the b asis of the cation mismatch introduced by barium substitution. (C) 1998 Els evier Science B.V. All rights reserved.