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In this paper, the effect of heat treatment on the structure and magnetic properties of the alloy is investigated by heat treating the melted Fe2Cr1-xMnxGa samples at different temperatures. It is found that the structure and magnetic properties of Fe2Cr1-xMnxGa are very sensitive to heat treatment and there is a certain degree of disorder. The structure of the prepared samples changes with different conditions of heat treatment, and the change in structure will in turn affect the magnetic behavior of the alloy. The magnetization intensity increases with increasing annealing temperature, indicating that the orderliness of the samples is improved by heat treatment. The magnetization intensity of the samples decreases with the doping of Mn content, which is due to the anti-parallel arrangement of the Fe-Mn spin magnetic moments by the doped Mn atoms. [ABSTRACT FROM AUTHOR]

The concept of topological quantum number, or topological charge, has been used extensively to describe topological defects or solitons. Nematic liquid crystals contain both integer and half-integer topological defects, making them useful models for testing the rules that govern topological defects. Here, we investigated topological defects in nematic liquid crystals using the phase-field method. If there are no defects along a loop path, the total charge number is described by an encircled loop integral. We found that the total charge number is conserved, and the conservation of defects number is determined by a boundary during the generation and annihilation of positive–negative topological defects when the loop integral is confined. These rules can be extended to other two-dimensional systems with topological defects. [ABSTRACT FROM AUTHOR]

Fully compensated ferrimagnets do not create any magnetic stray field and allow for a completely polarized current of charges. As a result, these alloys show promising prospects for applications as spintronic devices. In this paper, we investigated the phase stability, the site preference, the tetragonal distortion and the influence of symmetry from the crystal structure and chemical environments of magnetic ions on the magnetic properties of Cr2YZ and Mn2YZ (Y = void, Ni, Cu, and Zn; Z = Ga, Ge, and As) full Heusler alloys by first-principles calculations. We found that the selected Cr2-based alloys, except for Cr2NiGa and Cr2NiGe, prefer to crystallize in the centrosymmetric L21-type structure, while the selected Mn2-based alloys, except for Mn2CuAs, Mn2ZnGe and Mn2ZnAs, tend to crystallize in the non-centrosymmetric XA-type structure. Due to the symmetry, the antiferromagnetism of the selected L21-type alloys is very stable, and no spin-polarized density of states could be generated. In contrast, the magnetic moment of the selected XA-type alloys depends heavily on the number of valence electrons and tetragonal distortion, and spin-polarized density of states is generated. Therefore, the selected alloys with L21-type structures and their tetragonal-distorted structure are potential candidates for conventional antiferromagnets, while those with XA-type structure and their tetragonal-distorted structure are promising candidates for (fully) compensated ferrimagnets. [ABSTRACT FROM AUTHOR]

Nematic liquid crystals (LCs) normally contain both integer and half-integer topological charges. In this work, we investigate topological charge evolution dynamics in nematic LCs by the phase-field model. We observe the annihilation of the topological charge, and the total number of charges decreases to two cores with time evolution in a disk. A significant decrease in charges is observed during the initial evolution. The positive topological charge and negative topological charge annihilate depending on the distance between two charges, which can be treated as the interaction force. The form of interaction force is similar to Coulomb's law, but the force is inversely the distance of defects instead of the square of the distance in Coulomb's law. Therefore, the present study contributes to the understanding of topological charge evolution dynamics and provides guidance for experiments to design in nematic LCs. [ABSTRACT FROM AUTHOR]

Twinning is a common phenomenon in crystal growth and mechanical deformation. It plays a key role in tuning the mechanical and transport properties of metals. In transition metal oxides, the twinning may give additional changes related to magnetism. Herein, the atomic configuration and the electronic structure of the twin boundaries (TBs) in rock‐salt‐type NiO are studied, combining aberration‐corrected transmission electron microscopy and first‐principles calculations. For NiO, the twinning occurs on the (111) plane, with oxygen atoms located at the TB and antiferromagnetic (AFM) coupling between the mirroring Ni atomic planes near the TB. The configuration gives the TB energy of 0.26 J m−2. Atomic and magnetic structures of fivefold twins in NiO are also investigated. In the structure of fivefold twins with the lowest energy, ferromagnetic coupling is formed in the AFM TBs due to the competing exchange interaction at the core of fivefold twins. [ABSTRACT FROM AUTHOR]