Abstract
A spin tunnel junction based on manganites, with La1���xSrxMnO3 LSMO as ferromagnetic metallic electrodes
and the undoped parent compound LaMnO3 LMO as insulating barrier, is here theoretically discussed
using double-exchange model Hamiltonians and numerical techniques. For an even number of LMO layers, the
ground state is shown to have antiparallel LSMO magnetic moments. This highly resistive, but fragile, state is
easily destabilized by small magnetic fields, which orient the LSMO moments in the direction of the field. The
magnetoresistance associated with this transition is very large, according to Monte Carlo and density-matrix
renormalization group studies. The influence of temperature, the case of an odd number of LMO layers, and the
differences between LMO and SrTiO3 as barriers are also addressed. General trends are discussed.
