Imaging current-induced switching of antiferromagnetic domains in CuMnAs

The magnetic order in antiferromagnetic materials is hard to control with external magnetic fields. Using X-ray Magnetic Linear Dichroism microscopy, we show that staggered effective fields generated by electrical current can induce modification of the antiferromagnetic domain structure in microdevices fabricated from a tetragonal CuMnAs thin film. A clear correlation between the average domain orientation and the anisotropy of the electrical resistance is demonstrated, with both showing reproducible switching in response to orthogonally applied current pulses. However, the behavior is inhomogeneous at the submicron level, highlighting the complex nature of the switching process in multi-domain antiferromagnetic films

Toward mid-infrared, subdiffraction, spectral-mapping of human cells and tissue: SNIM (scanning near-field infrared microscopy) tip fabrication

Scanning near-field infrared microscopy (SNIM) potentially enables subdiffraction, broadband mid-infrared (MIR:3–25-μm wavelength range) spectral-mapping of human cells and tissue for real-time molecular sensing, with prospective use in disease diagnosis. SNIM requires an MIR-transmitting tip of small aperture for photon collection. Here, chalcogenide-glass optical fibers are reproducibly tapered at one end to form a MIR transmitting tip for SNIM. A wet-etching method is used to form the tip. The tapering sides of the tip are Al-coated. These Al-coated tapered-tips exhibit near-field power-confinement when acting either as the launch-end or exit-end of the MIR optical fiber. We report first time optimal cleaving of the end of the tapered tip using focused ion beam milling. A flat aperture is produced at the end of the tip, which is orthogonal to the fiber-axis and of controlled diameter. A FIB-cleaved aperture is used to collect MIR spectra of cells mounted on a transflection plate, under illumination of a synchrotron- generated wideband MIR beam

Current polarity-dependent manipulation of antiferromagnetic domains

Antiferromagnets have several favourable properties as active elements in spintronic devices, including ultra-fast dynamics, zero stray fields and insensitivity to external magnetic fields. Tetragonal CuMnAs is a testbed system in which the antiferromagnetic order parameter can be switched reversibly at ambient conditions using electrical currents. In previous experiments, orthogonal in-plane current pulses were used to induce 90° rotations of antiferromagnetic domains and demonstrate the operation of all-electrical memory bits in a multi-terminal geometry. Here, we demonstrate that antiferromagnetic domain walls can be manipulated to realize stable and reproducible domain changes using only two electrical contacts. This is achieved by using the polarity of the current to switch the sign of the current-induced effective field acting on the antiferromagnetic sublattices. The resulting reversible domain and domain wall reconfigurations are imaged using X-ray magnetic linear dichroism microscopy, and can also be detected electrically. Switching by domain-wall motion can occur at much lower current densities than those needed for coherent domain switching