Spin torque control of antiferromagnetic moments in NiO

Takahiro Moriyama,Motoi Kimata,Kent Oda,Takuo Ohkochi,Teruo Ono

doi:10.1038/s41598-018-32508-w

Abstract

For a long time, there were no efficient ways of controlling antiferromagnets. Quite a strong magnetic field was required to manipulate the magnetic moments because of a high molecular field and a small magnetic susceptibility. It was also difficult to detect the orientation of the magnetic moments since the net magnetic moment is effectively zero. For these reasons, research on antiferromagnets has not been progressed as drastically as that on ferromagnets which are the main materials in modern spintronic devices. Here we show that the magnetic moments in NiO, a typical natural antiferromagnet, can indeed be controlled by the spin torque with a relatively small electric current density (~4 × 107 A/cm2) and their orientation is detected by the transverse resistance resulting from the spin Hall magnetoresistance. The demonstrated techniques of controlling and detecting antiferromagnets would outstandingly promote the methodologies in the recently emerged “antiferromagnetic spintronics”. Furthermore, our results essentially lead to a spin torque antiferromagnetic memory.

Highlights

For a long time, there were no efficient ways of controlling antiferromagnets
The majority of spintronics research and applications has so far dealt with ferromagnetism, with much less attention given to antiferromagnetic materials
Theoretical and experimental studies have suggested that it is possible to control the antiferromagnetic moments by the spin transfer torque due to a consequence of the interaction between the local moment and the itinerant electron spins[3,4,5,6,7]

Summary

OPEN Spin torque control of antiferromagnetic moments in NiO

There were no efficient ways of controlling antiferromagnets. Quite a strong magnetic field was required to manipulate the magnetic moments because of a high molecular field and a small magnetic susceptibility. We show that the magnetic moments in NiO, a typical natural antiferromagnet, can be controlled by the spin torque with a relatively small electric current density (~4 × 107 A/ cm2) and their orientation is detected by the transverse resistance resulting from the spin Hall magnetoresistance. In order for our spin torque writing scheme (Fig. 1(a)) to work, the minimum requirement may be that the magnetic moments of the NiO need to lie in the sample plane and the staggered magnetic moments are coherent in the thickness direction. The post-processed monochrome images around the central area of the Hall cross shown in Fig. 3(e) clearly resolve the expansion of the NiO domain after the writing operation We stress that basic requirements for practical antiferromagnetic spintronic devices, i.e. the electrical control and detection of antiferromagnetic moments, are fulfilled

The multilayers were formed by magnetron sputtering on

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