J. Phys. I France
Volume 5, Numéro 4, April 1995
Page(s) 501 - 515
DOI: 10.1051/jp1:1995143
J. Phys. I France 5 (1995) 501-515

Magnetic Interactions In YbBa $_{\bf 2}$Cu $_{\bf 3}$O $_{\bf x}$ (x = 7.0, 6.0) From $^{\bf 170}$Yb $^{\bf 3+}$ Mössbauer Measurements

J.A. Hodges, P. Bonville, P. Imbert and A. Pinatel-Phillipot

CEA/DSM/DRECAM/Service de Physique de l'Etat Condensé, Centre d'Etudes de Saclay, 91191 Gif sur Yvette, France

(Received 19 October 1994, received in final form 19 December 1994, accepted 19 December 1994)

The magnetic interactions in superconducting YbBa 2Cu 3O 7 and non-superconducting YbBa 2Cu 3O 6 have been examined using 170Yb 3+ Mössbauer spectroscopy on grain-oriented samples. In YbBa 2Cu 3O 7 where the Yb 3+ sublattice orders at 0.35 K and the saturated magnetic moment is 1.75  $\mu_{\rm B}$, the saturated molecular field is 0.4 T and it is directed perpendicular to the c-axis. In YbBa 2Cu 3O 6, where the Cu(2) sublattice also orders, the average saturated molecular field on Yb 3+ is 0.2 T. It is disordered in direction and contains contributions from both the Yb 3+ and the Cu(2) 2+ sublattices. The presence of a Cu(2) 2+ derived molecular field shows the Yb 3+ ions are not at a center of magnetic inversion symmetry relative to the ordered Cu(2) 2+ moments.

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