Readout of an antiferromagnetic spintronics system by strong exchange coupling of Mn2Au and Permalloy

S P Bommanaboyena,M Jourdan,R M Reeve,T Denneulin,T Mashoff,B Sarpi,K Everschor-Sitte,Y R Niu,S S Dhesi,H.-J Elmers,D Backes,M Kläui,J Sinova,D Schönke,O Gomonay,L S I Veiga,A Kovács

doi:10.1038/s41467-021-26892-7

Abstract

In antiferromagnetic spintronics, the read-out of the staggered magnetization or Néel vector is the key obstacle to harnessing the ultra-fast dynamics and stability of antiferromagnets for novel devices. Here, we demonstrate strong exchange coupling of Mn2Au, a unique metallic antiferromagnet that exhibits Néel spin-orbit torques, with thin ferromagnetic Permalloy layers. This allows us to benefit from the well-established read-out methods of ferromagnets, while the essential advantages of antiferromagnetic spintronics are only slightly diminished. We show one-to-one imprinting of the antiferromagnetic on the ferromagnetic domain pattern. Conversely, alignment of the Permalloy magnetization reorients the Mn2Au Néel vector, an effect, which can be restricted to large magnetic fields by tuning the ferromagnetic layer thickness. To understand the origin of the strong coupling, we carry out high resolution electron microscopy imaging and we find that our growth yields an interface with a well-defined morphology that leads to the strong exchange coupling.

Highlights

In antiferromagnetic spintronics, the read-out of the staggered magnetization or Néel vector is the key obstacle to harnessing the ultra-fast dynamics and stability of antiferromagnets for novel devices
Mn2Au(001) was directly demonstrated by magnetic microscopy[16,17]. From these only two available compounds with a bulk Néel spin-orbit torque (NSOT), Mn2Au stands out concerning potential memory applications due to its metallic conductivity, high Néel temperature (>1000 K)[18], and magnetocrystalline anisotropy, which results in a long term room temperature stability of Néel vector aligned states[6]
We investigated the orientation of N and MF of a Mn2Au(40 nm)/Py(4 nm)/ SiNx(2 nm) sample by x-ray absorption spectroscopy (XAS), in the surfacesensitive total electron yield (TEY) as well as in the bulk sensitive substrate fluorescence yield (FY) mode

Summary

Introduction

The read-out of the staggered magnetization or Néel vector is the key obstacle to harnessing the ultra-fast dynamics and stability of antiferromagnets for novel devices. Regarding the manipulation of the Néel vector orientation, the application of short current pulses creating spin-orbit torques (SOT) is a promising approach These can be created at interfaces with heavy metal layers[7,8,9] or for metallic compounds in the bulk of the AFM itself[10]. In the latter case, only CuMnAs and Mn2Au have been identified to combine the required crystallographic and magnetic structure with strong spin-orbit coupling, such that a current along a specific direction can create a bulk Néel spin-orbit torque (NSOT) acting on the Néel vector[10]. From these only two available compounds with a bulk NSOT, Mn2Au stands out concerning potential memory applications due to its metallic conductivity, high Néel temperature (>1000 K)[18], and magnetocrystalline anisotropy, which results in a long term room temperature stability of Néel vector aligned states[6]

Methods

Results

Conclusion