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Type: Artigo de periódico
Title: Possible anisotropy gap in La1.35Sr1.65Mn2O7 and La1.5Sr0.5NiO4 detected through specific heat and magnetization measurements
Author: Lopez, J
de Lima, OF
Abstract: Magnetization and specific heat measurements, as a function of temperature, were performed on single crystals of La1.35Sr1.65Mn2O7 and La1.5Sr0.5NiO4, under different applied magnetic fields (H). The specific heat in La1.35Sr1.65Mn2O7 was decreased for H = 9 T parallel to the crystal c axis, compared with H = 0, possibly due to a suppression of spin-wave excitations (magnons) in that ferromagnetic bilayer structure. On the other hand, the applied magnetic field had no effect in the specific heat of the antiferromagnetic La1.5Sr0.5NiO4. For H = 9 T and below the temperature of 4 K the specific heat data, for each crystal, was well fitted by an exponential decay law. This allowed the calculation of energy gaps around I meV for both compounds, in close agreement with Delta = 2 mu H-B for an expected energy gap in the magnon spectrum. Detailed magnetization measurements showed monotonic variations below 4 K and a steep increase close to 2 K. Both magnetization and specific heat measurements suggest the existence of an anisotropy gap in the energy spectrum of La1.35Sr1.65Mn2O7 and La1.5Sr0.5NiO4. (c) 2006 Elsevier Ltd. All rights reserved.
Subject: magnetic perovskites
anisotropy gap
heat capacity
Country: Inglaterra
Editor: Pergamon-elsevier Science Ltd
Rights: fechado
Identifier DOI: 10.1016/j.ssc.2006.06.017
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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