The universal oscillation of the tunnel magnetoresistance (TMR) ratio as a function of the insulating barrier thickness in crystalline magnetic tunnel junctions (MTJs) is a long-standing unsolved problem in condensed matter physics. To explain this, we here introduce a superposition of wave functions with opposite spins and different Fermi momenta, based on the fact that spin-flip scattering near the interface provides a hybridization between majority- and minority-spin states. In a typical Fe/MgO/Fe MTJ, we solve the tunneling problem and show that the TMR ratio oscillates with a period of ∼3\r{A} by varying the MgO thickness, consistent with previous and present experimental observations.
@article{arxiv.2406.07919,
title = {Theory for Tunnel Magnetoresistance Oscillation},
author = {Keisuke Masuda and Thomas Scheike and Hiroaki Sukegawa and Yusuke Kozuka and Seiji Mitani and Yoshio Miura},
journal= {arXiv preprint arXiv:2406.07919},
year = {2025}
}