In search of zero magnetostrictive CoFeB/AlOx/Co junctions

This study examines two kinds (as-deposited and annealed) of magnetic tunnel junctions (MTJs): glass / CoFeB ( t A ) / AlO x ( δ t o ) / Co ( t B ) with t A + t B = 150 Å , t B = 50 , 70, 75, and 100 Å; and δ t o = 0 – 30 Å . After field-annealing these MTJs at T A = 250 ∘ C for 1 h, the concave up feature, originally existing in the magnetostriction ( λ s ) vs. δ t o curve, turns into the fluctuating feature. We have successfully determined the composition of the zero- λ s MTJ, 〈 t B o 〉 or t B o , with or without annealing, as a function of δ t o , which appears to be important technical information.