Electromotive force and huge magnetoresistance in magnetic tunnel junctions

Pham Nam Hai, Shinobu Ohya, Masaaki Tanaka, Stewart Barnes, Sadamichi Maekawa

Research output: Contribution to journalArticle

123 Citations (Scopus)

Abstract

The electromotive force (e.m.f.) predicted by Faradays law reflects the forces acting on the charge,-e, of an electron moving through a device or circuit, and is proportional to the time derivative of the magnetic field. This conventional e.m.f. is usually absent for stationary circuits and static magnetic fields. There are also forces that act on the spin of an electron; it has been recently predicted that, for circuits that are in part composed of ferromagnetic materials, there arises an e.m.f. of spin origin even for a static magnetic field. This e.m.f. can be attributed to a time-varying magnetization of the host material, such as the motion of magnetic domains in a static magnetic field, and reflects the conversion of magnetic to electrical energy. Here we show that such an e.m.f. can indeed be induced by a static magnetic field in magnetic tunnel junctions containing zinc-blende-structured MnAs quantum nanomagnets. The observed e.m.f. operates on a timescale of approximately 10 2-10 3 seconds and results from the conversion of the magnetic energy of the superparamagnetic MnAs nanomagnets into electrical energy when these magnets undergo magnetic quantum tunnelling. As a consequence, a huge magnetoresistance of up to 100,000 per cent is observed for certain bias voltages. Our results strongly support the contention that, in magnetic nanostructures, Faradays law of induction must be generalized to account for forces of purely spin origin. The huge magnetoresistance and e.m.f. may find potential applications in high sensitivity magnetic sensors, as well as in new active devices such as spin batteries.

Original languageEnglish (US)
Pages (from-to)489-492
Number of pages4
JournalNature
Volume458
Issue number7237
DOIs
StatePublished - Mar 26 2009

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Magnetic Fields
Electrons
Equipment and Supplies
Magnets
Nanostructures
Zinc

ASJC Scopus subject areas

  • General

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Electromotive force and huge magnetoresistance in magnetic tunnel junctions. / Hai, Pham Nam; Ohya, Shinobu; Tanaka, Masaaki; Barnes, Stewart; Maekawa, Sadamichi.

In: Nature, Vol. 458, No. 7237, 26.03.2009, p. 489-492.

Research output: Contribution to journalArticle

Hai, PN, Ohya, S, Tanaka, M, Barnes, S & Maekawa, S 2009, 'Electromotive force and huge magnetoresistance in magnetic tunnel junctions', Nature, vol. 458, no. 7237, pp. 489-492. https://doi.org/10.1038/nature07879
Hai, Pham Nam ; Ohya, Shinobu ; Tanaka, Masaaki ; Barnes, Stewart ; Maekawa, Sadamichi. / Electromotive force and huge magnetoresistance in magnetic tunnel junctions. In: Nature. 2009 ; Vol. 458, No. 7237. pp. 489-492.
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