| Autor: |
Oseroff, S. B., Moreno, N. O., Pagliuso, P. G., Rettori, C., Huber, D. L., Gardner, J. S., Sarrao, J. L., Thompson, J. D., Causa, M. T., Alejandro, G., Tovar, M., Alascio, B. R. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 5/1/2000, Vol. 87 Issue 9, p5810, 3p |
| Abstrakt: |
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 La[sub 1.2]Sr[sub 1.8]Mn[sub 2]O[sub 7], 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), ΔH[sub pp](T)=[C/Tχ(T)]ΔH[sub pp](∞). The high temperature limit of the linewidth, ΔH[sub pp](∞), 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, ΔH[sub pp](∞)∝ω[sub p][sup 2]/J where J is proportional to the Curie–Weiss temperature, including the hybridization mechanism producing CMR. Instead, ΔH[sub pp](∞) 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 La[sub 1.2]Sr[sub 1.8]Mn[sub 2]O[sub 7], a bilayer compound, although isotropic at high temperatures, becomes anisotropic for T[sub c]=125 K
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| Databáze: |
Complementary Index |
| Externí odkaz: |
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