Magnetic and magnetotransport properties of 3D interconnected NiCo/Cu and Co/Cu multilayered nanowire networks

Magnetic nanowires present a new field of research. Nanowire networks are studied because of their interesting properties and great potential in numerous applications including data storage, high frequency devices, microwave absorption, resistive switching memories, as well as catalyser, medical devices and batteries. More and more fabrication techniques are developed, always looking to improve their properties. Electrodeposition appears to be an elegant, versatile and cheap method to create nanowire networks. It allows for measurements in the current perpendicular to plane geometry thanks to a template made of a porous polycarbonate membrane. Multilayered crossed nanowire networks show interesting giant magnetoresistance properties. To study these properties, it is necessary to observe the magnetic behaviour first. In the case of nanowires, this behaviour is mainly governed by shape anisotropy and dipolar interactions. These properties are present both at individual nanowire level and at network level. As a consequence, the characterisation of the individual and global properties of the networks is of utmost importance to understand the behaviour correctly before producing new devices. This master thesis is the continuity of a previous work studying Nickel-Cobalt/Copper multilayered crossed nanowires. Very high giant magnetoresistance values were obtained, but those could not be reproduced reliably. The samples presented in this work show stable and reproducible results but with slightly reduced GMR values. The electrodeposition uses electrolytes with lower concentrations of materials than in the previous work. These electrolytes were elaborated to enable homogeneous depositions without blocking the templates' pores. The results are satisfying, as good GMR results are obtained with low sample-to-sample variability. The multilayered crossed nanowires are made of ferromagnetic layers composed of Cobalt or Cobalt-Nickel alloys, and non-magnetic layers composed of Copper. The composition of the ferromagnetic layers is analysed with a scanning electron microscope. Two types of templates are used, with different porosities and nanowire diameters. For the higher porosity template, Cobalt appears to be better suited. For the lower porosity template, the Nickel-Cobalt alloy delivers higher giant magnetoresistance values - and even more so at low temperature.