Structural, electronic, and magnetic properties of MnSi and Mn4Si7 nanowires

Abstract

The importance of nanoscale magnetism under tailored phase evolution has been gaining considerable interest in the past few decades, attributable to the surging demand for memory devices and emerging electromagnetism. Herein, we present experimental demonstrations and theoretical studies on the structural, electronic, and magnetic properties of MnSi and Mn4Si7 nanowires grown by thermal chemical vapor deposition. The crystallinity of the nanowires was confirmed by a high-resolution transmission electron microscope and elemental distribution. The ratio of Mn to Si (∼0.96–1.04) indicates uniformity in MnSi composition. Additionally, the Mn4Si7 nanowire has an Mn/Si ratio of ∼0.78–0.87, which deviates from the homogenous Mn4Si7 ratio of ∼ 0.6 due to a higher Mn content at the nucleation sites. We found that the MnSi nanowires remained ferromagnetic (FM), similar to bulk MnSi, whereas the Mn4Si7 nanowires exhibited an FM order in contrast to the non-magnetic nature of bulk Mn4Si7. Field-cooled and zero-field-cooled magnetization curves reveal that the Mn4Si7 nanowires exhibited an FM order with a transition temperature (Tc) above room temperature. In contrast, the MnSi nanowires have a lower Tc of ∼ 30 K. It is noting that the First-principles density functional theory calculations demonstrated that both MnSi and Mn4Si7 nanowires possess a metallic characteristic. The spin-charge density of Mn4Si7 nanowires was found to be localized near the surface, implying a surface-induced magnetism. These findings suggest the possibility of tunning the phase evolution of Si-based nanowires by simply changing the diffusion mechanism of the Mn precursor. These metallic nanowires may be used as nanoscale interconnects and gate electrodes in nanoscale technologies.