Electron spin resonance and magnetization in perovskite and pyrochlore manganites

Abstract

We have performed electron spin resonance (ESR) and dc susceptibility, χdc(T), measurements in La0.7Ca0.3MnO3 perovskite up to 1000 K. This is adequately described in the paramagnetic regime in the constant coupling approximation assuming an effective Heisenberg-like pair interaction. The ESR linewidth is given by ΔHpp(T)=ΔHpp(∞)[C/Tχ(T)]. The ESR intensity follows the T dependence of χdc(T). We conclude that the relaxation mechanism is essentially the same for the whole studied paramagnetic range. The observed behavior reflects the progressive importance of magnetic clustering on approaching Tc. We have found similar T dependence for La0.7Sr0.3MnO3 and La0.7Pb0.3MnO3 perovskites, and also for the pyrochlore In2Mn2O7.