Tunnel magnetoresistance

In physics, the tunnel magnetoresistance effect, commonly abbreviated as TMR, occurs when two ferromagnets are separated by a thin (about 1 nm) insulator. Then the resistance of the tunneling current changes with the relative orientation of the two magnetic layers. The resistance is normally higher in the anti-parallel case.

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It was discovered in 1975 by Michel Julliere, using iron as the ferromagnet and germanium as the insulator.

Room temperature TMR was discovered in 1995 first by Terunobu Miyazaki and independently by Moodera et al. following renewed interest in this field fueled by the discovery of the giant magnetoresistive effect. It is now the base for the magnetic random access memory (MRAM) and read sensors in hard disk drives. For more technical information see [Moodera and Mathon 1999].

References

M. Julliere (1975). "Tunneling between ferromagnetic films". Phys. Lett. 54A: 225-226. sciencedirect

T. Miyazaki and N. Tezuka (1995). "Giant magnetic tunneling effect in Fe/Al₂O₃/Fe junction". J. Magn. Magn. Mater. 139: L231-L234. mit

J. S. Moodera et al. (1995). "Large Magnetoresistance at Room Temperature in Ferromagnetic Thin Film Tunnel Junctions". Phys. Rev. Lett. 74: 3273–3276. aps

G. Binasch et al. (1989). "Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange". Phys. Rev. B 39: 4828–4830. aps