Thermal variations of the Jahn–Teller effect in a CMR manganite La0.7Ca0.3MnO3 and charge and magnetic ordering in 57Fe doped rare earth manganite

Abstract

Domain fluctuations at low temperature are evidenced in perovskite-type rare earth manganites by two local methods: X-ray absorption and Mössbauer spectroscopies. For the CMR compound La0.7Ca0.3MnO3, the thermal variations of the prepeak at the O K-edge, obtained by XAS measurements, show that the large prepeak observed at 300 K becomes a double peak below 200 K. These shape changes are very smooth and gradual around Tc and indicate the existence of FMM domain fluctuations around the PMI–FMM transition temperature. For Sm0.5Ca0.5MnO3 doped with 1.5% 57Fe, the Mössbauer spectra evidence charge and magnetic ordering phenomena below Tco≈270 K. The magnetic transition, spread on a large temperature domain, is attributed to fluctuations in the antiferromagnetic state.