Julliere TMR ratio: (R_AP − R_P)/R_P = 2 P₁P₂ / (1 − P₁P₂)

Julliere 1975 tunneling-magnetoresistance ratio for a magnetic tunnel junction (MTJ) with two ferromagnetic electrodes separated by an insulating barrier. Assuming spin-conserving elastic tunneling at Fermi energy: TMR = (R_AP − R_P)/R_P…