EMR Probing of Magnetic Ordering in ${rm Pr}_{1-x}{rm Sr}_{x}{rm MnO}_{3}$ ( $x=$ 0.22, 0.24, 0.26) Manganite Single Cryst

摘要

To probe magnetic ordering in single crystals of ${rm Pr}_{1-x}{rm Sr}_{x}{rm MnO}_{3}$ ($x=$ 0.22, 0.24, 0.26), the $X$-band electron magnetic resonance (EMR) measurements were carried out in the temperature range 5 K $leq{rm T}leq $ 600 K. It appears that two additional (as compared to well-known ${rm La}_{1-x}{rm Ca}_{x}{rm MnO}_{3}$ system) factors influence on such ordering and on magnetic correlations in paramagnetic state. They are: low temperature ferromagnetic like order of Pr-subsystem and strong charge ordered state (CO). In particular, the competition of CO and ferromagnetic coupling results in suppression of EMR susceptibility at low temperatures, as well as in its notable deviation from the standard Curie-Weiss behavior in paramagnetic state. It is shown that the character of paramagnetic spin dynamics changes notably with Sr-doping, i.e., the higher doping—the stronger contribution of electron-impurity spin relaxation mechanism.