Quasi two-dimensional magnetic order of Tb3+ spins in Pb2Sr2Tb1−x Ca x Cu3O8 (x = 0 and 0.5) |
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Authors: | U. Staub L. Soderholm S. Skanthakumar S. Rosenkranz C. Ritter W. Kagunya |
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Affiliation: | 1. Swiss Light Source Project, Paul Scherrer Institute, CH-5232, Villigen PSI, Switzerland 2. Chemistry Division, Argonne National Laboratory, Argonne, IL, 60439, USA 3. Laboratory for Neutron Scattering, ETH & PSI, CH-5232, Villigen PSI, Switzerland 4. Institut Laue Langevin, 156 X, F-38042, Grenoble Cedex, France 5. ISIS, Rutherford Appleton Laboratory, Didcot, OX11 0KX, UK
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Abstract: | Neutron diffraction experiments were performed to study the magnetic ordering of the Tb+3 sublattice in the high-T c superconductor Pb2Sr2Tb1?x Ca x Cu3O8 (x = 0.5) and the undoped parent compound (x = 0). For the parent compound, a quasi two dimensional (2D) phase with a finite antiferromagnetic correlation along the c-direction and a three dimensional phase with ferromagnetic correlation along the c-direction were found. The coexistence of the two phases is likely to be related to structural imperfections such as stacking faults, strains, oxygen disorder or cation vacancies. The superconductor with a superconducting transition temperature of T c = 71K exhibits a quasi 2D magnetic ordering of the Tb sublattice with a finite ferromagnetic correlation along the c-direction. The correlation lengths along the c-direction for the quasi 2D phases are 32 and 26Å for x = 0 and 0.5, respectively. The magnetic saturation moments are with 9.1 and 8.8 μ B in excellent agreement with our mean-field crystal-field calculations. 2D short range correlation could be observed up to about 8T N and is described by a Lorentzian distribution of magnetic intensity perpendicular to the 2D rod in reciprocal space. |
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