Magnetic characterization of lambda-MnO2 and Li2Mn2O4 prepared by electrochemical cycling of LiMn2O4

Magnetic characterization has been performed on the cubic phases lambda-Li0 .07Mn2O4, Li0.98Mn2O4, and the tetragonal phase Li1.82Mn2O4, prepared by el ectrochemical cycling of a single starting LiMn2O4 spinel. The magnitude of the negative Weiss constant increases with x in LixMn2O4, indicating that antiferromagnetic interactions increase in strength as the Mn4+ concentrati on decreases. Spin-glass behavior is observed in all three materials, as pr eviously seen in nearly stoichiometric LiMn2O4 [Jang et al., Appl. Phys. Le tt. 74, 2504 (1999)]. A short-range antiferromagnetic correlation is observ ed in Li2Mn2O4 at temperatures below the paramagnetic temperature regime, w hich is ascribed to collective Jahn-Teller distortion causing a two-dimensi onal nearest-Mn-neighbors interaction. (C) 2000 American Institute of Physi cs. [S0021-8979(00)05910-7].