1D Nanomaterials in Fe‐Group Metals Obtained by Synthesis in the Pores of Polymer Templates: Correlation of Structure, Magnetic, and Transport Properties

Abstract

1D cylindrical magnetic nanostructures (FeNi, FeCo, FeCoP) of complex topology such as nanowires (NWs), nanotubes (NTs), multilayered nanowires, and core–shell structures are discussed from the perspective of engineering a wide variety of magnetic materials from hard to semihard to soft. Most of recent data are given for the materials synthesized in the pores of polymer ion‐track membranes, which makes it possible to tune systematically the geometrical parameters, morphology, and composition. The key properties including crystal and micromagnetic structure, magnetic anisotropy, and coercivity are analyzed. Co‐based NWs with uniform morphology demonstrate coercivity of more than 10 kOe due to the combination of crystalline and shape anisotropies. In the case of NTs, the demagnetizing effect is reduced owing to a helical arrangement of the magnetization, which leads to low values of coercivity and remanence magnetization. Varying the geometrical parameters of multilayered NWs, the alternating soft and semihard magnetic layers can be made within a single nanowire, which is important for spin‐valve magnetoresistance. Au‐coated ferromagnetic nanostructures are biocompatible and can be used to enhance optical absorption. Ni@Au NTs used as substrates for Raman spectroscopy demonstrate the enhancement factor of the order of 104. Some aspects related to applications of 1D magnets are briefly overviewed.