Evidence of spin frustration in LaMnO3+δ with δ=0.0 and 0.025

We measured the ac susceptibility and the de magnetization of LaMnO3+delta with delta = 0.0 and 0.025. The ac susceptibility showed a clear frequency dependence near the Neel temperature T-N for both samples. Furthermore, the de magnetization showed that LaMnO3.0 had a non-zero isothermal remanent magnetization below 140 K. From both measurements, we conclude that the antiferromagnetic transition of LaMnO3+delta is accompanied by the development of an order parameter of ferromagnetic nature, which has almost the same transition temperature as T-N. We discuss our results in terms of a possible phase coexistence at a microscopic level.