Intrinsic spin dynamics in optically excited nanoscale magnetic tunnel junction arrays restored by dielectric coating

We report the all-optical observation of intrinsic spindynamics and extraction of magnetic material parameters from arrays of sub-100  nm spin-transfer torque magnetic random access memory (STT-MRAM) devices with a CoFeB/MgO interface. To this end, the interference ofsurface acoustic waves with time-resolved magneto-optic signals via magneto-elastic coupling was suppressed using adielectric coating. The efficacy of this method is demonstrated experimentally and via modeling on anickelnanomagnet array. Themagnetization dynamics for both coatednickel and STT-MRAM arrays shows a restored field-dependent Kittel mode from which the effective damping can be extracted. We observe an increased low-field damping due to extrinsic contributions from magnetic inhomogeneities and variations in thenanomagnet shape, while the intrinsic Gilbert damping remains unaffected bypatterning. The data are in excellent agreement with a local resonance model and have direct implications for the design of STT-MRAM devices as well as other nanoscale spintronic technologies.

Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: M. Jaris, Y. Yahagi, B. K. Mahato, S. Dhuey, S. Cabrini, V. Nikitin, J. Stout, A. R. Hawkins and H. Schmidt Source Type: research