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Two types of quantum-dot circuits measuring a Hamming distance using the Coulomb repulsion effect are proposed and analysed. They have structures where a quantum-dot array is arranged on a gate electrode of an ultrasmall MOSFET. The device parameters for successful operation are clarified from Monte Carlo simulation.

Small Fe particles of nm size were formed in MgO films by a codeposition technique. Static magnetization and ferromagnetic resonance were measured. Magnetic couplings between the particles are discussed on the basis of experimental data of ferromagnetic resonance and magnetization measurement. The data show that the particles in high Fe concentration film are strongly coupled, while those in low concentration films consist of two types of particles: strongly coupled ones and independent ones. Static magnetization measurement strongly suggests enhanced magnetism at the interface of the Fe particles and MgO matrix, which has been theoretically predicted.