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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|
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.|
|Editor:||Pergamon-elsevier Science Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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