Change of universality class of metal-insulator transition due to magneticordering

Using a two-band model we report a theory to describe the metal-insulator ( MI) transition as a function of an external applied magnetic field in Kondo insulators. To deal with electronic correlations we use a functional integ ral approach in the static approximation. We show the existence of a critic al value of the Coulomb correlation U-c, such that for U<U-c the MI transit ion is continuous and occurs from a paramagnetic insulator to a paramagneti c metal. In this case this transition is in the universality class of densi ty-driven transitions. For U>U-c, the transition is to a ferromagnetic meta l and it is described by different critical exponents. (C) 1999 American In stitute of Physics. [S0021-8979(99)77108-2].