Site-resolved contributions to the magnetic anisotropy energy and complex spin structure of Fe/MgO sandwiches

CUADRADO, Ramón, OROSZLÁNY, László, DEÁK, András, OSTLER, Thomas, MEO, Andrea, CHEPULSKII, Roman, APALKOV, Dmytro, EVANS, Richard, SZUNYOGH, László and CHANTRELL, Roy (2018). Site-resolved contributions to the magnetic anisotropy energy and complex spin structure of Fe/MgO sandwiches. Physical Review Applied, 9 (054048).

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Fe/MgO-based Magnetic Tunnel Junctions (MTJs) are among the most promising candidates for spintronic devices due to their high thermal stability and high tunneling magnetoresistance. Despite its apparent simplicity, the nature of the interactions between the Fe and MgO layers leads to complex finite size effects and temperature dependent magnetic properties which must be carefully controlled for practical applications. In this letter, we investigate the electronic, structural and magnetic properties of MgO/Fe/MgO sandwiches using first principles calculations and atomistic spin modeling based on a fully parameterized spin Hamiltonian. We find a large contribution to the effective interfacial magnetic anisotropy from the two-ion exchange energy. Minimization of the total energy using atomistic simulations shows a surprising spin spiral ground state structure at the interface owing to frustrated ferromagnetic and antiferromagnetic interactions, leading to a reduced Curie temperature and strong layer-wise temperature dependence of the magnetization. The different temperature dependences of the interface and bulk-like layers results in an unexpected non-monotonic temperature variation of the effective magnetic anisotropy energy and temperature-induced spin-reorientation transition to an in-plane magnetization at low temperatures. Our results demonstrate the intrinsic physical complexity of the pure Fe/MgO interface and the role of elevated temperatures providing new insight when interpreting experimental data of nanoscale MTJs.

Item Type: Article
Research Institute, Centre or Group - Does NOT include content added after October 2018: Materials and Engineering Research Institute > Advanced Coatings and Composites Research Centre
Departments - Does NOT include content added after October 2018: Faculty of Science, Technology and Arts > Department of Engineering and Mathematics
Identification Number:
Depositing User: Thomas Ostler
Date Deposited: 26 Apr 2018 09:01
Last Modified: 18 Mar 2021 12:31

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