Appearance of Griffiths-Like Phase in a New Pyrochlore Compound La2Mn2O7−δ.

The La₂Mn₂O_{7 − δ} compound was prepared using ceramic method. The X-ray diffraction study revealed that this compound crystallized in pyrochlore oxide–type monoclinic structure with the P2/M space group. Concerning the magnetization measurements, they showed a paramagnetic (PM) behavior at high temperature and a ferromagnetic (FM) transition near 167 K. As for the magnetic measurements, they demonstrated the possible existence of a Griffiths-like phase, which was observed for the first time, to our knowledge, in a pyrochlore oxide-type A₂B₂O₇. This originality can be due to the competition between the AFM and FM interactions of the Mn ions, induced by oxygen deficiency. The critical isotherm analyses indicated that the 3D-Heisenberg was the most acceptable model in the case of our compound. [ABSTRACT FROM AUTHOR]