Unveiling new magnetic phases of undoped and doped manganites

Hotta, Takashi; Moraghebi, M.*; Feiguin, A.*; Moreo, A.*; Yunoki, Seiji*; Dagotto, E.*

Novel ground-state spin structures in undoped and doped manganites are here investigated based on the orbital-degenerate double-exchange model, by using mean-field and numerical techniques. In undoped manganites, a new antiferromagnetic (AFM) state, called the E-type phase, is found adjacent in parameter space to the A-type AFM phase. Its structure is in agreement with recent experimental results. This insulating E-AFM state is competing with a ferromagnetic metallic phase as well, suggesting that large magneto-resistant effects could exist even in undoped manganese oxides. For doped layered manganites, the phase diagram includes another new AFM phase of the -type. Experimental signatures of the new phases are discussed.