ELECTRONIC SPIN RESONANCE STUDY OF PEROVSKITE-TYPE MANGANITES

The electron spin resonance behavior of two typical systems with Mn3+ /Mn4+=2∶1 and 1∶1 within the temperature range T>TC is s tudied experimentally. The results show that there exists a temperature Tmi n(>TC)dividing the magnetic behavior above TC into t wo distinguishable regime. While T>Tmin, The ESR spectrum consists of one symmetrical resonance line. The Lande factor is independent of temperature and close to the value of free electron (20023) and the linewidth increase s linearly with increasing temperature. Some distortions are observed when the t emperature is lower than Tmin. The line shape becomes unsymmetrical. The g factor become dependent on the temperature and the linewidth increases ano malously with decreasing temperature. These results point out that the complete paramagnetism exits only in the temperature range T>Tmin. When T Cmin,the anomalous paramagnetic behavior may be caused by t he magnetic inhomogeneity. The mechanism of resonance linewidth broadening is di scussed based on an analysis of the linewidth above Tmin, suggesting that the exchange narrowing spin-spin interaction and the spin-lattice interacti on are two possible reasons of linewidth changes in the high temperature regime.