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Observation of Magnetic Hysteresis at the Nanometer Scale by Spin-Polarized Scanning Tunneling Spectroscopy

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Science  15 Jun 2001:
Vol. 292, Issue 5524, pp. 2053-2056
DOI: 10.1126/science.1060513

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Abstract

Using spin-polarized scanning tunneling microscopy in an external magnetic field, we have observed magnetic hysteresis on a nanometer scale in an ultrathin ferromagnetic film. An array of iron nanowires, being two atomic layers thick, was grown on a stepped tungsten (110) substrate. The microscopic sources of hysteresis in this system—domain wall motion, domain creation, and annihilation—were observed with nanometer spatial resolution. A residual domain 6.5 nanometers by 5 nanometers in size has been found which is inherently stable in saturation fields. Its stability is the consequence of a 360° spin rotation. With magnetic memory bit sizes approaching the superparamagnetic limit with sub–10 nanometer characteristic lengths, the understanding of the basic physical phenomena at this scale is of fundamental importance.

  • * To whom correspondence should be addressed. E-mail: pietzsch{at}physnet.uni-hamburg.de

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