Magnetic structures in colossal magnetoresistance perovskites (abstract)

Ferromagnetism in colossal magnetoresistance perovskites such as LaxB1-xMnO3 (B=Ba,Sr,Ca) is typically explained using the double exchange (DE) mechanism proposed by Zener. To explain the local structure above Tc one needs to introduce a coupling to lattice degrees of freedom. Here, we show the structure of the resulting magnetoelastic polarons and the temperature dependence of their pair potential. To investigate the open-quotes ferroclose quotes-magnetic state below Tc we study the ferromagnetic Kondo lattice model in the strong coupling limit. It turns out that the DE mechanism has unexpected properties, when there is more than one itinerant electron. We find that in general, the many-body ground state of the DE model is not globally ferromagnetically ordered. Also, the low-energy excitations of this model are distinct from spin wave excitations in usual Heisenberg ferromagnets, which will result in unusual dynamic magnetic properties. copyright 1997 American Institute of Physics