KAUST RepositoryWe predict that a lateral electrical current in antiferromagnets can induce nonequilibrium Néel-order fields, i.e., fields whose sign alternates between the spin sublattices, which can trigger ultrafast spin-axis reorientation. Based on microscopic transport theory calculations we identify staggered current-induced fields analogous to the intraband and to the intrinsic interband spin-orbit fields previously reported in ferromagnets with a broken inversion-symmetry crystal. To illustrate their rich physics and utility, we consider bulk Mn 2 Au with the two spin sublattices forming inversion partners, and a 2D square-lattice antiferromagnet with broken structural inversion symmetry modeled by a Rashba spin-orbit coupling. We propose an antiferromagnetic memory device with electrical writing and reading.

One of the main obstacles that prevents practical applications of antiferromagnets is the difficulty of manipulating the magnetic order parameter. Recently, following the theoretical prediction [J. Zelezný et al., PRL 113, 157201 (2014)], the electrical switching of magnetic moments in an antiferromagnet has been demonstrated [P. Wadley et al., Science 351, 587 (2016)]. The switching is due to the so-called spin-orbit torque, which has been extensively studied in ferromagnets. In this phenomena a non-equilibrium spin-polarization exchange coupled to the ordered local moments is induced by current, hence exerting a torque on the order parameter. Here we give a general systematic analysis of the symmetry of the spin-orbit torque in locally and globally non-centrosymmetric crystals. We study when the symmetry allows for a nonzero torque, when is the torque effective, and its dependence on the applied current direction and orientation of magnetic moments. For comparison, we consider both antiferromagnetic and ferromagnetic orders. In two representative model crystals we perform microscopic calculations of the spin-orbit torque to illustrate its symmetry properties and to highlight conditions under which the spin-orbit torque can be efficient for manipulating antiferromagnetic moments.

The formation of ordered complex structures is one of the most challenging fields in the research of biomimic materials because those structures are promising with respect to improving the physical and mechanical properties of man-made materials. In this letter, we have developed a novel approach to fabricating complex structures on the mesoscale by combining magnetic-field-induced locomotion and supramolecular-interaction-assisted immobilization. We have employed a magnetic field to locomote the glass fiber, which was modified by the layer-by-layer self-assembly of magnetic nanoparticles, to desired positions and have exploited the supramolecular interaction to immobilize glass fiber onto the appointed position. By magnetically induced micromanipulation, we can drive another fiber across the former one and finally obtain a crossing structure, which can lead to more complex structures on the mesocale. Moreover, we have constructed a mesoscale structure, termed "CHEM", to demonstrate further the application of this method.

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