Letter abstract


Nature Nanotechnology 2, 631 - 634 (2007)
Published online: 16 September 2007 | doi:10.1038/nnano.2007.292



There is a Corrigendum (January 2008) associated with this Letter.

Subject term: Nanomagnetism and spintronics

Magnetic exchange bias of more than 1 Tesla in a natural mineral intergrowth

Suzanne A. McEnroe1, Brian Carter-Stiglitz2, Richard J. Harrison3, Peter Robinson1, Karl Fabian1 & Catherine McCammon4


Magnetic exchange bias is a phenomenon whereby the hysteresis loop of a ‘soft’ magnetic phase is shifted by an amount HE along the applied field axis owing to its interaction with a ‘hard’ magnetic phase. Since the discovery of exchange bias fifty years ago1, the development of a general theory has been hampered by the uncertain nature of the interfaces between the hard and soft phases, commonly between an antiferromagnetic phase and a ferro- or ferrimagnetic phase. Exchange bias continues to be the subject of investigation because of its technological applications and because it is now possible to manipulate magnetic materials at the nanoscale2, 3, 4, 5, 6. Here we present the first documented example of exchange bias of significant magnitude (>1 T) in a natural mineral. We demonstrate that exchange bias in this system is due to the interaction between coherently intergrown magnetic phases formed through a natural process of phase separation during slow cooling over millions of years. Transmission electron microscopy studies show that these intergrowths have a known crystallographic orientation with a known crystallographic structure and that the interfaces are coherent7, 8, 9, 10, 11, 12, 13, 14.

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  1. Geological Survey of Norway, N-7491, Trondheim, Norway
  2. Institute for Rock Magnetism, Newton Horace Winchell School of Earth Sciences, University of Minnesota, Minneapolis 55455, USA
  3. Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
  4. Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany

Correspondence to: Suzanne A. McEnroe1 e-mail: suzanne.mcenroe@ngu.no



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