Low-temperature specific heat of Er2Ba4Cu7O15-δ |
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Authors: | G Böttger P Allenspach A Dönni Y Aoki H Sato |
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Institution: | 110. Laboratory for Neutron Scattering, Eidgen?ssische Technische Hochschule Zürich & Paul Scherrer Institut, CH-5232, Villigen PSI, Switzerland 210. National Research Institute for Metals, Tsukuba, Ibaraki 305, Japan 310. Department of Physics, Faculty of Science, Tokyo Metropolitan University, Hachioji-shi, 192-03, Japan
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Abstract: | The magnetic ordering of Er ions in Er2Ba4Cu7O15-δ (δ = 0:7 and δ = 0:08) has been studied by low temperature heat capacity measurements. The Néel temperature T N of Er2Ba4Cu7O15-δ is almost independent of the oxygen concentration (TN = 0:54K for δ = 0:08 and T N = 0:50K for δ = 0:7). While an anisotropic two-dimensional (2D) Ising model describes the experimental data very well for Er2Ba4Cu7O14:92, this model cannot be applied to the oxygen reduced sample Er2Ba4Cu7O14:3. By using a model consisting of 1D-Ising chains and of 2D-Ising clusters of Er3+ ions we could fit the specific heat data of Er2Ba4Cu7O14:3 accurately. Our measurements show clearly that with the reduction of the oxygen content the in-plane anisotropy of the magnetic exchange coupling increases. |
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