Current density-induced emergence of soft and hard magnetic phases in Fe nanowire arrays

The capability of generating magnetically soft and hard phases in a material is important in many aspects, ranging from basic science to applications. Here, the emergence of soft and hard magnetic phases is reported in Fe nanowire (NW) arrays with a diameter of 35 nm fabricated by using a pulsed electrochemical deposition method in porous aluminum oxide templates under different current density (C) values in the range of 25-100 mA cm^-2. The variation ofCinfluences the grain size, crystallinity, electrodeposition efficiency and length of the Fe NWs, as characterized by x-ray diffraction, high-resolution transmission electron microscopy, vibrating sample magnetometry and field-emission scanning electron microscopy. IncreasingCfrom 25 to 80 mA cm^-2results in a significant decrease in coercivity and squareness from 1590 to 900 Oe and 0.9 to 0.5, respectively, inducing the soft and hard phases along the length of Fe NWs. Further increasing theCleads to the separation of the phases, as evidenced by first-order reversal curve analysis. From a theoretical aspect, the emergence of the soft phase may lead to the occurrence of the fanning reversal mode in the NWs, for which there is no precedent in previous experimental investigations.