Crystallographic phases in La2/3Ba1/3MnO3: temperature transformations and relation to magnetism

The structural and magnetic analysis of polycrystalline samples of La2/3Ba1/3MnO3 has been carried out between 5 and 370 K by means of neutron-diffraction technique and DC magnetic measurements. Below the Curie point TC=314 K the system undergoes a structural phase transition R3barc-Imma. The transition extends over a wide temperature range, proceeds most rapidly in the vicinity of Tm=200 K, and has characteristic features of a martensitic phase transition. The uniaxial pressure effect on the DC magnetization is maximal at 200 K. Two magnetic phase transitions (of the second order at 250 K and of the First order at 177.5 K) are reflected mainly in the R3barc phase crystal parameters