Publication

Manipulation of Néel vector in antiferromagnetic Mn2Au by electric current and magnetic field pulses

Authors: Stanislav Bodnar (Johannes Gutenberg-Universität Mainz)
Co-authored by industrial partner: No

Type: Thesis

State: Published (Approved)
Published: August 2020

Abstract: In antiferromagnetic spintronics the Néel vector corresponding to the staggered magnetization is used to encode information. In the framework of spin-based electronics, antiferromagnets as active elements have a number of advantages compared to ferromagnetic materials: The natural spin dynamics of antiferromagnets in the THz range is of major significance as it makes this class of magnetic materials promising for ultrafast switching as well as for the generation and detection of THz radiation. Furthermore, the lack of net magnetization of antiferromagnets makes their Néel vector oriented state robust with respect to external magnetic fields. This property results in a high stability of the information encoded in the Néel vector orientation, which cannot be destroyed by external magnetic fields. Last but not least, antiferromagnets do not produce stray fields, which are limiting the minimum feasible size of data storage units based on ferromagnets. However, the lack of net magnetization makes the manipulation of the Néel vector orientation much more challenging than the corresponding manipulation of the magnetization of ferromagnets. One of the possible approaches is based on a current induced bulk spin-orbit torque, which was predicted to exist for very specific crystal structures of collinear antiferromagnets, the so-called Neel spin-orbit torque. Only two antiferromagnetic compounds with the required crystal structure are known up to now: Mn2Au, on which this work is focused, and CuMnAs. In my thesis, I investigate the effects of current pulses on the antiferromagnetic domain structure which is modified by a Néel vector reorientation originating from Néel spin-orbit torques and alternative effects. As an alternative Néel vector manipulation method, I also investigate the switching of the Néel vector orientation in Mn2Au by the application of very large high magnetic field pulses causing a spin-flop transition. To investigate current induced Néel vector switching in Mn2Au, I performed electric transport measurements where I measured current-induced changes of the resistance of up to 6% and compared the results with calculations of our collaboration partners. In order to directly visualize the Néel vector reorientation, we performed photoelectron emission microscopy experiments with magnetic contrast combined with transport measurements. During this experiment, massive changes of the AFM domain pattern induced by current pulses were observed. Also the reorientation of the Néel vector induced by magnetic field pulse driven spin-flop transitions was correlated with magnetotransport measurements. Here, persistent changes of the resistance associated with anisotropic magnetoresistance and a transient drop of the resistance in the range of 2% were obtained. These experiments demonstrated Néel vector switching in Mn2Au both by a current induced Néel spin-orbit torque mechanism and by a magnetic field induced spin-flop transition. It was shown that the magnetoresistance of the antiferromagnetic domain walls in Mn2Au plays a crucial role in the understanding of current-induced resistance modifications associated with Néel vector switching processes. Additional to transient effects, there are as well persistent resistance modifications induced by the Neel vector reorientation , which is an essential property for data storage applications.

Subject Areas: Physics, Materials


Instruments: I06-Nanoscience

Added On: 09/09/2020 14:50

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