Ferromagnetic polarons in dilute La-doped Ca2RuO4

Ca2RuO4 is an antiferromagnetic insulator with a Neel temperature at T-N = 110K and a Mott transition at T-MI = 357 K. Slight substitution of trivalen t La for divalent Ca in Ca2RuO4 not only drastically reduces T-MI but also simultaneously precipitate robust ferromagnetism in the antiferromagnetic h ost. It is believed that the ferromagnetic behavior is closely associated w ith the kinetic energy of the electron added from the La ion that modifies the magnetic structure, and as a result, forming ferromagnetic polarons in the antiferromagnetic background. These dramatic changes underline the subt lety of the competition between the antiferromagnetic and ferromagnetic cou pling in Ca2RuO4. (C) 2001 Published by Elsevier Science B.V.