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Subject: antiferromagnetism ×

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    Exchange Bias Effect of Ni@(NiO,Ni(OH)2) Core/Shell Nanowires Synthesized by Electrochemical Deposition in Nanoporous Alumina Membranes
    (Basel : MDPI, 2023) García, Javier; Gutiérrez, Ruth; González, Ana S.; Jiménez-Ramirez, Ana I.; Álvarez, Yolanda; Vega, Víctor; Reith, Heiko; Leistner, Karin; Luna, Carlos; Nielsch, Kornelius; Prida, Víctor M.
    Tuning and controlling the magnetic properties of nanomaterials is crucial to implement new and reliable technologies based on magnetic hyperthermia, spintronics, or sensors, among others. Despite variations in the alloy composition as well as the realization of several post material fabrication treatments, magnetic heterostructures as ferromagnetic/antiferromagnetic coupled layers have been widely used to modify or generate unidirectional magnetic anisotropies. In this work, a pure electrochemical approach has been used to fabricate core (FM)/shell (AFM) Ni@(NiO,Ni(OH)2) nanowire arrays, avoiding thermal oxidation procedures incompatible with integrative semiconductor technologies. Besides the morphology and compositional characterization of these core/shell nanowires, their peculiar magnetic properties have been studied by temperature dependent (isothermal) hysteresis loops, thermomagnetic curves and FORC analysis, revealing the existence of two different effects derived from Ni nanowires’ surface oxidation over the magnetic performance of the array. First of all, a magnetic hardening of the nanowires along the parallel direction of the applied magnetic field with respect their long axis (easy magnetization axis) has been found. The increase in coercivity, as an effect of surface oxidation, has been observed to be around 17% (43%) at 300 K (50 K). On the other hand, an increasing exchange bias effect on decreasing temperature has been encountered when field cooling (3T) the oxidized Ni@(NiO,Ni(OH)2) nanowires below 100 K along their parallel lengths.
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    Topological Weyl semimetals in the chiral antiferromagnetic materials Mn3Ge and Mn3Sn
    (Milton Park : Taylor & Francis, 2017) Yang, Hao; Sun, Yan; Zhang, Yang; Shi, Wu-Jun; Parkin, Stuart S.P.; Yan, Binghai
    Recent experiments revealed that Mn3Sn and Mn3Ge exhibit a strong anomalous Hall effect at room temperature, provoking us to explore their electronic structures for topological properties. By ab initio band structure calculations, we have observed the existence of multiple Weyl points in the bulk and corresponding Fermi arcs on the surface, predicting antiferromagnetic Weyl semimetals in Mn3Ge and Mn3Sn. Here the chiral antiferromagnetism in the Kagome-type lattice structure is essential to determine the positions and numbers of Weyl points. Our work further reveals a new guiding principle to search for magnetic Weyl semimetals among materials that exhibit a strong anomalous Hall effect.