Thermal variations of the Jahn–Teller effect in a CMR manganite La0.7Ca0.3MnO3and charge and magnetic ordering in 57Fe doped rare earth manganite

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 Tcand indicate the existence of FMMdomain fluctuations around the PMI–FMMtransition temperature. For Sm0.5Ca0.5MnO3doped 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.