Spin dynamics in perovskites, pyrochlores, and layered manganites

S. B. Oseroff, N. O. Moreno, P. G. Pagliuso, C. Rettori, D. L. Huber, J. S. Gardner, J. L. Sarrao, J. D. Thompson, M. T. Causa, G. Alejandro, M. Tovar, B. R. Alascio

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Abstract

High temperature electron spin resonance (ESR) and magnetic susceptibility (χ) are analyzed for manganites related with colossal magnetoresistance (CMR). The properties of compounds with different crystalline structures: three-dimensional (3D) perovskites, pyrochlore, and La1.2Sr1.8Mn2O7, a two-dimensional layer, are compared. In the paramagnetic regime, and outside the critical regions associated with phase transitions, the temperature dependence of the ESR linewidth presents a universal behavior dominated by the variations of χ(T), ΔHpp(T) = [C/Tχ(T)]ΔHpp(∞). The high temperature limit of the linewidth, ΔHpp(∞), is related to the parameters of the Hamiltonian describing the interactions of the spin system. The role played by magnetic anisotropy, isotropic superexchange, and double exchange is revealed and discussed in the analysis of the experimental data. In CMR and non-CMR pyrochlores, ΔHpp(∞)∝ω2p/J where J is proportional to the Curie-Weiss temperature, including the hybridization mechanism producing CMR. Instead, ΔHpp(∞) of CMR perovskites seems not to be affected by the double-exchange interaction. In contrast with the 3D perovskites, the ESR linewidth and resonance field of La1.2Sr1.8Mn2O7, a bilayer compound, although isotropic at high temperatures, becomes anisotropic for Tc= 125 K<T<Tp≈450 K.

Original languageEnglish
Pages (from-to)5810-5812
Number of pages3
JournalJournal of Applied Physics
Volume87
Issue number9 II
DOIs
StatePublished - May 2000
Externally publishedYes
Event44th Annual Conference on Magnetism and Magnetic Materials - San Jose, CA, United States
Duration: Nov 15 1999Nov 18 1999

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