Origin of Magnetization Decay in Spin-Dependent Tunnel Junctions

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Science  12 Nov 1999:
Vol. 286, Issue 5443, pp. 1337-1340
DOI: 10.1126/science.286.5443.1337

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Spin-dependent tunnel junctions based on magnetically hard and soft ferromagnetic layers separated by a thin insulating barrier have emerged as prime candidates for information storage. However, the observed instability of the magnetically hard reference layer, leading to magnetization decay during field cycling of the adjacent soft layer, is a serious concern for future device applications. Using Lorentz electron microscopy and micromagnetic simulations, the hard-layer decay was found to result from large fringing fields surrounding magnetic domain walls in the magnetically soft layer. The formation and motion of these walls causes statistical flipping of magnetic moments in randomly oriented grains of the hard layer, with a progressive trend toward disorder and eventual demagnetization.

  • * To whom correspondence should be addressed. E-mail: molly.mccartney{at}

  • Present address: Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK.

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