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Broadband Ferromagnetic Resonance Linewidth Measurement of Magnetic Tunnel Junction Multilayers



Stephen E. Russek, Ranko R. Heindl, William H. Rippard, Juan F. Sierra, F G. Aliev


Magnetic tunnel junction multilayer films have been characterized with broadband ferromagnetic resonance (FMR) over a frequency range of 1 to 20 GHz.  Tunnel junctions were fabricated using Al2O3 tunnel barriers and CoFeB/NiFe free layers and underwent a sequence of anneals at various temperatures.  It was found that the FMR linewidth of the free layer increases near the regions of free layer reversal and fixed layer reversal.  The increase in FMR linewidth correlates with the magnetization hysteresis curves in unpatterned films, the low frequency noise in patterned devices, and previous observations of ripple using Lorentz microscopy. The large increase in free layer linewidth and its subsequent change upon annealing indicates that considerable disorder, originating in the exchange-biased fixed layer, is transferred to the free layer.  The disorder gives rise to spatially varying magnetostatic fields and to a large extrinsic damping. The FMR linewidth of the free layer is shown to be a simple and useful diagnostic of the quality of the magnetic structure and interfaces in magnetic tunnel junctions.
Applied Physics Letters


magnetic tunnel junctions, ferromagnetic resonance, FMR, FMR linewidth


Russek, S. , Heindl, R. , Rippard, W. , Sierra, J. and Aliev, F. (2009), Broadband Ferromagnetic Resonance Linewidth Measurement of Magnetic Tunnel Junction Multilayers, Applied Physics Letters, [online], (Accessed July 16, 2024)


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Created January 7, 2009, Updated February 19, 2017