Atomic-Orbital and Plane-Wave Approaches to Ferromagnetic Properties of Ni x Fe 1-x Nanowires
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Atomic-Orbital and Plane-Wave Approaches to Ferromagnetic Properties of NixFe1-x Nanowires Ikram Ziti1,2, M. R. Britel2 and Chumin Wang1 1 2
Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, CDMX 04510, Mexico National School of Applied Sciences, Abdelmalik Esaadi University, Tangier, Morocco
ABSTRACT There are growing interests on magnetic nanowires, due to their potential applications in magnetic sensors and recording devices. In this work, we report a comparative ab-initio study based on the Density Functional Theory (DFT) of NixFe1-x nanowire periodic arrays by using atomic-orbital and plane-wave basis respectively through DMol3 and CASTEP codes. After performing the geometry optimization, we calculate the spin-polarized electronic density of states, average interatomic distance, and magnetic moments. For pure Ni nanowires ( x 1) , the dependence of the magnetic moment obtained from CASTEP calculations on the cutoff energy, as well as that from DMol3 on the thermal smearing parameter is analyzed in detail. Both abinitio calculations predict close magnetic moments for each x, being slightly larger those of DMol3 obtained with significantly less computing cost. Finally, these DFT results are compared with experimental data and a good agreement is observed. INTRODUCTION The study of almost one-dimensional magnetic nanowires (NW) is greatly motivated by its distinctive properties that make them an interesting and useful material, especially for the biotechnology [1,2], high-density magnetic storage [3] and giant magnetoresistance devices [4]. The tunable magnetic and chemical properties of nanowires make them an excellent vehicle for applying forces to cells. Transition metals are widely used in such NWs because of their low cost in comparison with rare earth materials. In the last three decades, NixFe1-x NWs have been the central components of many technologies, such as magnetic sensors and recording devices, mainly due to their excellent magnetic softness with very high initial permeability and low coercivity [5]. The investigation on the variation of properties through shaping has captured enormous research interests. Many experimental studies have shown enhanced magnetic properties of NWs with different diameter [6] and compositions [7]. In particular, NixFe1-x nanowire arrays can be fabricated by the electrodeposition technique into nano-porous alumina template. The magnetic moment of nanowires can be measured by means of vibrating sample magnetometer (VSM) [6] or superconducting quantum interference device (SQUID) magnetometer [8]. On the theoretical side, there are essentially two paths for modelling the magnetic properties of solids. The first one is the semi-empirical approach, which has the advantage of being simple and capable to study complex structures. However, this approach involves parameters whose variation in nanostructures is difficult to be predicted. In this work, we choose the second one through ab-initio calculations. This approach is particularly suitable
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