Computer simulation of magnetization flop in magnetic tunnel junctions exchange-biased by synthetic antiferromagnets |
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| Institution: | 1. National Synchrotron Radiation Centre Solaris, Jagiellonian University, 30-392 Kraków, Poland;2. Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, 30-239 Kraków, Poland;3. AGH University of Science and Technology, Academic Centre for Materials and Nanotechnology, 30-055 Kraków, Poland;4. AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, 30-059 Kraków, Poland;1. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA;2. National High Magnetic Field Laboratory, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA;3. Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;1. Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA;2. Department of Physics, Oakland University, Rochester, MI 48309, USA;1. Institute of Health and Wellbeing, University of Glasgow, 1 Lilybank Gardens, Glasgow, G12 8RZ, UK;2. Institute of Cardiovascular and Medical Sciences, University of Glasgow, BHF Glasgow Cardiovascular Research Centre, 126 University Place, Glasgow, G12 8TA, UK;1. Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China;2. Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, P. R. China;3. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, P. R. China;1. Department of Physics, Universitas Gadjah Mada, Yogyakarta, Indonesia;2. Departemen of Physics, Universitas Kristen Satya Wacana, Salatiga, Indonesia |
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| Abstract: | Computer simulation in a single domain multilayer model is used to investigate magnetization flop in magnetic tunnel junctions, exchange-biased by pinned synthetic antiferromagnets with the multilayer structure NiFe/AlOx/Co/Ru/Co/FeMn. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy and hence increased coercivity of the Co layers in the synthetic antiferromagnet. However, when the synthetic antiferromagnet is not or weakly pinned, the magnetization directions of the two layers sandwiching AlOx, which mainly determine the magnetoresistance, are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal MR change from the high MR state to zero, irrespective of the direction of the free layer switching. This emphasizes an importance of a strong pinning of the synthetic antiferromagnet at small cell dimensions. The threshold field for magnetization flop is found to increase linearly with increasing antiferromagnetic exchange coupling between the two Co layers in the synthetic antiferromagnet. The restoring force from magnetization flop to the normal synthetic antiferromagnetic structure is roughly proportional to the resistance to magnetization flop. Irrespective of the magnetic parameters and cell sizes, the state of magnetization flop does not exist near Ha=0, indicating that magnetization flop is driven by the Zeeman energy. |
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