High-temperature spin dynamics in CMR manganites: ESR and magnetization

M.T. CAUSA; M. TOVAR; A. CANEIRO; F. PRADO; G. IBAÑEZ; C. RAMOS; A. BUTERA; B. ALASCIO; X. OBRADORS; S. PIÑOL; F. RIVADULA; C. VAZQUEZ-VAZQUEZ; M.A. LÓPEZ QUINTELA; J. RIVAS; Y. TOKURA; S. OSEROFF

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 1998 vol. 58 p. 3233 - 3239

1098-0121

We have performed electron spin resonance ~ESR! and dc susceptibility measurements in Mn perovskites upto 1000 K. Assuming an effective Heisenberg-like interaction for Mn312Mn41 spin pairs, the dc susceptibility,xdc(T), is well described in the paramagnetic regime by the constant coupling approximation. Absolutedetermination of the ESR intensity indicates that all Mn spins contribute to the ESR line in the temperaturerange studied. The ESR linewidth can be described by DHpp(T)5DHpp(`) @C/Txdc(T)#, thus presenting auniversal behavior in a temperature scale normalized to Tc . A single relaxation mechanism, related to spinonlyinteractions, explains the T dependence of DHpp(T) for all the compounds studied: La0.67Ca0.33MnO3,La0.67Sr0.33MnO3, Pr0.67Sr0.33MnO3, and La0.67Pb0.33MnO3. The dc susceptibility and the ESR linewidth andintensity all reflect the progressive importance of magnetic clustering below '2Tc .