Spin Transfer in an
Antiferromagnet
PAPER: Z. Wei, A. Sharma,
A. S. Nunez, P. M. Haney, R. A. Duine, J. Bass, A. H. MacDonald, and M.
Tsoi, Changing Exchange Bias in Spin
Valves with an Electric Current, Phys.
Rev. Lett. 98, 116603 (2007)
PREPRINT: Wei, Z.,
Sharma, A., Nunez, A. S., Haney, P. M., Duine, R. A., Bass, J., MacDonald, A.
H., and Tsoi, M. Spin transfer in an antiferromagnet. Preprint cond-mat/0606462
SLIDES: French-US
Workshop on Spintronics
Saint
Pierre de Chartreuse, France, June 12-13, 2006
ABSTRACT:
An electrical current can
transfer spin angular momentum to a ferromagnet1-3. This novel
physical phenomenon, called spin transfer, offers unprecedented spatial and temporal
control over the magnetic state of a ferromagnet and has tremendous potential
in a broad range of technologies, including magnetic memory and recording.
Recently, it has been predicted4 that spin transfer is not limited
to ferromagnets, but can also occur in antiferromagnetic materials and even be
stronger under some conditions. In this paper we demonstrate transfer of spin
angular momentum across an interface between ferromagnetic and
antiferromagnetic metals. The spin transfer is mediated by an electrical
current of high density (~1012 A/m2) and revealed by
variation in the exchange bias at the ferromagnet/antiferromagnet interface. We
find that, depending on the polarity of the electrical current flowing across
the interface, the strength of the exchange bias can either increase or
decrease. This finding is explained by the theoretical prediction that a spin
polarized current generates a torque on magnetic moments in the
antiferromagnet. Current-mediated variation of exchange bias can be used to control
the magnetic state of spin-valve devices, e.g., in magnetic memory
applications.
1.
Slonczewski, J.
C. Current-driven excitation of magnetic multilayers. J. Magn. Magn. Mater. 159,
L1-L7 (1996).
2.
Berger, L.
Multilayer as spin-wave emitting diodes. J.
Appl. Phys. 81, 4880-4882
(1997).
3.
Tsoi, M. et al. Excitation of a magnetic
multilayer by an electric current. Phys.
Rev. Lett. 80, 4281-4284 (1998).
4.
Núñez, A. S.,
Duine, R. A., Haney, P. M., and MacDonald, A. H. Theory of spin torques and
giant magnetoresistance in antiferromagnetic metals. Preprint cond-mat/0510797, to appear in Phys. Rev. B.
This work was supported
in part by the Welch Foundation, by DOE grant DE-FG03-02ER45958, and by NSF
grants DMR-05-01013 and DMR-06-45377