Magnetic structures and magnetic susceptibilities of terbium oxysulfide and oxyselenide |
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Authors: | Y. Abbas J. Rossat-Mignod G. Quezel |
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Affiliation: | Laboratoire de Diffraction Neutronique - D.R.F., Centre d''Etudes Nucléaires, Grenoble, France;Laboratoire de Magnétisme, C.N.R.S., Grenoble, France |
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Abstract: | For the two isomorphous compounds Tb2O2S and Tb2O2Se, the magnetic susceptibility measurements on powder samples show an antiferromagnetic ordering with Néel temperatures of about 7.7 and 7K respectively. Differing in this respect from the other rare earth oxyselenides, the magnetic anisotropy of Tb2O2Se at low temperature is weaker than that of Tb2O2S.We also determine the magnetic structures of these two compounds by neutron diffraction experiments at 1.5K. The magnetic cell is orthohexagonal and doubled along the c-axis; the magnetic moments make an angle, with the c-axis, of 47 ± 10° for Tb2O2S and 30 ± 10° for Tb2O2Se and the moment values at 1.5K are 8.14 ± 0.2μB and 6.5 ± 0.2μB, respectively.It is rather exceptional that in a rare earth uniaxial compound the magnetic moment makes an angle with the c-axis. However we interpret this situation by the fact that several levels exist very near to the ground state. The crystal field calculations are in good agreement with the experimental results. |
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