We study the effects of temperature and magnetic field on a two-orbital
Hubbard model within dynamical mean field theory. We focus on the quarter
filled system, which is a special point in the phase diagram due to orbital
degeneracy. At this particular filling the model exhibits two different
long-range order mechanisms, namely orbital order and ferromagnetism. Both can
cooperate but do not rely on each other's presence, creating a rich phase
diagram. Particularly, in the vicinity of the phase transition to an orbitally
ordered ferromagnetic state, we observe a strong magnetoresistance effect.
Besides the low temperature phase transitions, we also observe a crossover
between a paramagnetic insulating and a paramagnetic metallic state for
increasing Hund's coupling at high temperatures.Comment: 7 pages, 7 figure
