We have studied the potential energy and effective field induced by the presence of a single superparamagnetic particle above a magnetic domain wall in a 5 nm ferromagnetic film (Ms = 800 emu/cm3) with uniaxial crystalline anisotropy (Ku < 107 erg/cm3). The wall width, wall type (head-to-head, Néel, and perpendicular Bloch), film dimensions, particle height, and external applied field are found to affect the performance of particle sensing systems. Results and optimization strategies derived from this model are presented. The calculated change in depinning field (ΔHdp) is compared against experimental data and micromagnetic simulation. This comparison provides justification for further development in terms of integration with micromagnetic simulations.

We propose a complete, quantitative quantum computing system that satisfies the five DiVincenzo criteria. The model is based on magnetic clusters with uniaxial anisotropy, where two-state qubits are formed utilizing the two lowest lying states of an anisotropic potential energy. We outline the quantum dynamics required by quantum computing for single-qubit structures, and then define a measurement scheme in which qubit states can be measured by sharp changes in current as voltage across the cluster is varied. We then extend the single-qubit description to multiple qubit interactions, facilitated specifically by an entanglement method that propagates the controlled-not quantum gate.INDEX TERMS Magnetic clusters (MC), quantum computation, quantum engineering.

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