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Electrochemical depositions directed towards the development of magnetoelectronic devices
As dimensions of a metallic conductor are reduced so that conduction electrons pass without scattering, electric transport becomes ballistic. This ultimately leads to conductance quantization, revealing a quantum-mechanical nature of electrons and a conductor width comparable to an electron's wavelength, i.e. a fraction of a nanometer. In ferromagnetic metals, properties of electrons such as their wavelength depend on their spin angular momentum, which results in spin-dependent conductance quantization and leads to unusual magnetoresistive (MR) phenomena. One of them is ballistic anisotropic magnetoresistance (BAMR), a quantized change in the ballistic conductance according to the direction of magnetization. We observed BAMR in Co electrodeposited nanocontacts by in-situ investigation of their spin-dependent transport properties. By measuring the conductance as a function of the applied magnetic field direction at saturation, we found the step-wise variation of the ballistic conductance, signature of the BAMR effect. The experimental results showed that BAMR could be positive and negative, and exhibited symmetric and asymmetric angular dependences, which was consistent with the theoretical predictions. This BAMR phenomenon may be appealing for the future generation of electronic devices, such as quantum switches and logic circuits, adding the possibility to control the quantized conductance by applied magnetic fields. ^ Based on the same junction, other structures such as alternating multilayers of ferromagnetic metal (FM) and nonmagnetic metal (NM) and FM-NM-FM trilayer point contacts were investigated by the same methods. Bismuth point contacts on gold substrates showed bulk bismuth properties with large ordinary magnetoresistance (OMR). The Ni-Bi-Ni point contacts showed small OMR due to the bad interface between Ni and Bi. Point contacts of Co/Cu multilayer and Co-Cu-Co trilayer were also studied and showed not negligible MR, which reveals the possibility of making GMR electronic devices in nanocontact geometries. ^
Zhang, Chunjuan, "Electrochemical depositions directed towards the development of magnetoelectronic devices" (2007). ETD collection for University of Nebraska - Lincoln. AAI3274755.