X-ray absorption spectroscopy and photoemission study of Bi-doped LaMnO3

The magnetic property of Bi-doped LaMnO3 was studied from perspective of valence state and local distortion given by XPS and XAFS. An isotrivalent Mn3+ is proved to be existed in samples by XPS due to trivalent Bi3+ ions doped LaMnO3. Compared to the traditional ferromagnetic-paramagnetic phase transition with double exchange interaction between mixed valence states, this phase transition in our samples with isotrivalent Mn ions is understood by superexchange interaction in the way of Mn K-edge XAFS. A net ferromagnetic moment exists when the Mn-O-Mn bond angle deviates from 180°. The regular pattern of magnetization with doping concentration is related to the disorder degree of Mn-O and Mn-Mn pairs.