Production of magnetic nano wires by electrodeposition technique and their properties

Recently, the effect of magnetoimpedance (MI) has been used in technology such as magnetic field sensor, force sensor, current sensor and biosensor. The production of sensors as small as possible inevitable with developing technology. Some of the developed MI sensor has a nanoTesla resolution, but the smallest developed MI sensor has 2-3mm length. Therefore, in this thesis, magnetoimpedance properties of magnetic nanowires were studied. First, NiFe and CoNiFe nanowires were grown in highly ordered porous anodic alumina oxide (AAO) templates by dc electrodeposition. During the deposition process some electrochemical bath parameters such as ion content, pH, deposition voltage, and temperature of solution were kept constant. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that wires have diameters of about 250-310 nm and length 25-40 µm. Second, electrical contacts were made on both sides of the nanowire array and their magnetoimpedance (MI) properties were investigated. All the MI curves showed single peak behavior due to the high shape anisotropy. The maximum MI change at the 79 MHz driving current frequency was 1.45 % for NiFe nanowires. The maximum MI change at the 33 MHz driving current frequency was 2.72 % for CoNiFe nanowires. The magnitude of MI first increases and after a sharp peak, it starts to decrease with increasing driving current frequency. Finally, metal contacts to single NiFe nanowire was obtained using focused ion beam (FIB) system, the MI properties of single nanowire was also investigated. Although the MI change at low frequency was under 1 %, it was approached to 3.5 % at the 4 GHz. Maximum MI change was again decreased at higher frequencies.