Strain-induced shape anisotropy in antiferromagnetic structures

We demonstrate how shape-dependent strain can be used to control antiferromagnetic order in NiO/Pt thin films. For rectangular elements patterned along the easy and hard magnetocrystalline anisotropy axes of our film, we observe different domain structures and we identify magnetoelastic interactions that are distinct for different domain configurations. We reproduce the experimental observations by modeling the magnetoelastic interactions, considering spontaneous strain induced by the domain configuration, as well as elastic strain due to the substrate and the shape of the patterns. This allows us to demonstrate and explain how the variation of the aspect ratio of rectangular elements can be used to control the antiferromagnetic ground-state domain configuration. Shape-dependent strain does not only need to be considered in the design of antiferromagnetic devices, but can potentially be used to tailor their properties, providing an additional handle to control antiferromagnets.

Figure 1

(a) XMLD-PEEM image of shape-induced NiO domains inside a rectangular-shaped element, with its edges oriented along the in-plane projection of the easy axis. (b) Sketch of the experimental setup and orientation of the observed different Néel vector directions $[\pm 5\pm 519]$ with respect to the polarization vector. An orientation along $\left[5519\right]$ (yellow) is equally possible, but was not observed in this particular element.

Figure 2

(a) XMLD images of different NiO(10)/Pt(2) rectangular devices with varying aspect ratio. The edges of the devices are oriented along the in-plane projection of the easy axes. The arrows show the in-plane projection of the Néel vector determined from the grayscale contrast. (b) Final equilibrium state of the magnetic texture after considering magnetoelastic interactions to simulate the domain distribution in different aspect ratios. The color code indicates the direction of the Néel vector.

Figure 3

Comparison between equilibrium states with (a) and without (b) consideration of magnetoelastic coupling.

Figure 4

(a) Antiferromagnetic domain structure of a rectangular-shaped element oriented along the in-plane projections of the hard axes. (b) Simulated equilibrium state of the magnetic texture. The color code and the arrows indicate the direction of the Néel vector.

Figure 5

Sketch of the different direction of the rotation for strain at inner and outer corners.

Figure 6

Simulated evolution of the domain structure from the initial state to the final equilibrium state.

Figure 7

(a) X-ray absorption spectrum and XMLD for linear polarized x rays in the vicinity of the $L_2$ edge. (b) X-ray absorption spectrum and XMCD for circular polarized x rays.

Figure 8

Simulated and experimental contrast of the different domains dependent on the beam polarization for (a) $\gamma =-{30}^{\circ }$ and (b) $\gamma ={45}^{\circ }$.