钙钛矿Mn基氧化物的电子顺磁共振行为的实验研究

借助电子顺磁共振技术，对Mn³⁺/Mn⁴⁺=2∶1和1∶1的两个典型体系 在居里温度T_C以上温区的顺磁行为进行了实验研究.实验表明，存在一特征温度 T_min，通过该温度将T_C以上的磁行为分成两个明显可区分的温区： 在T_min以上，共振谱由一对称的单线构成，Lande 因子g值与温度无关且接近 自由电子的值(～20023)，线宽随温度呈线性变化等；而在T_{min关键词： 稀土锰氧化物 电子顺磁共振 交换变窄 自旋-自旋相互作用 自旋-晶格相互作用}

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>T_C is s tudied experimentally. The results show that there exists a temperature T_{mi n}(>T_C)dividing the magnetic behavior above T_C into t wo distinguishable regime. While T>T_min, The ESR spectrum consists of one symmetrical resonance line. The Lande factor is independent of temperature and close to the value of free electron (～20023)， and the linewidth increase s linearly with increasing temperature. Some distortions are observed when the t emperature is lower than T_min. 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>T_min. 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 T_min, 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.