Interplay between structure and magnetic properties in a perovskite manganite

Neutron powder diffraction and magnetization measurements have been carried out as a function of temperature in La1−xCaxMnO3 with x=0.18x=0.18. At room temperature, this sample is paramagnetic and single phase, with crystallographic symmetry Pnma (the longest axis is b-axis). It is observed that the c-axis becomes shorter than the a-axis below Curie temperature Tc, resulting in the enhancement of Q2-type Jahn–Teller (JT) distortion. Q2-type JT distortion mode is observed in the low-temperature ferromagnetic state for the present system, which is inconsistent with the theoretical prediction. Our results also provide evidence that the modifications in the structure around Mn atomic sites, are intimately related to the magnetic transition of this system.