Abstract
Tetragonal CuMnAs is an antiferromagnetic material with favourable properties for applications in spintronics. Using a combination of neutron diffraction and x-ray magnetic linear dichroism, we determine the spin axis and magnetic structure in tetragonal CuMnAs, and reveal the presence of an interfacial uniaxial magnetic anisotropy. From the temperature-dependence of the neutron diffraction intensities, the Néel temperature is shown to be (480 ± 5) K. Ab initio calculations indicate a weak anisotropy in the (ab) plane for bulk crystals, with a large anisotropy energy barrier between in-plane and perpendicular-to-plane directions.
Highlights
Tetragonal CuMnAs is an antiferromagnetic material with favourable properties for applications in spintronics
Several techniques exist for probing AF order in bulk crystals, of which neutron diffraction is the principal technique for the atomic level understanding of AF order
In the case of thin films, the only established direct probe of AF order is x-ray magnetic linear dichroism (XMLD), which is the angular-dependence of the absorption of linearly polarized x-rays
Summary
Mn and Cu L2,3 x-ray absorption edge spectra were obtained using the total electron yield method, with x-rays at normal incidence In this configuration, the angle-dependence of the x-ray polarization vector is sensitive to magnetic or structural anisotropies in the plane of the layer. The XMLD signal follows the same power-law dependence as the [100] neutron diffraction peak for the thicker CuMnAs film, shown by the black line in both Figs 2(c) and 3(d). For this calculation we did not include the relativistic spin-orbit coupling. Since magneto-elastic effects tend to be rather strong in AF materials, our results should be considered a lower bound for the expected anisotropy energies
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