MAGNETORESISTANCE OSCILLATIONS DUE TO CHANGING EFFECTS IN DOUBLE FERROMAGNETIC TUNNEL-JUNCTIONS

Electron tunneling in a double junction consisting of two ferromagneti c electrodes, with a small ferromagnetic metallic grain in between, is analyzed theoretically in the Coulomb blockade regime. A new phenomen on, that of oscillations in tunneling magnetoresistance due to discret e charging effects, is predicted. The corresponding oscillation period depends on the charging energy, and the oscillations disappear when b oth junctions have the same spin asymmetry. The interplay of the oscil lations and a nonoscillatory voltage dependence of the magnetoresistan ce is also analyzed. [S0031-9007(97)05142-9].