Spin-Topology and Quantum Magnetics in Nano-Structured Magnetic Materials

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This study is on the spin-topology and quantum magnetics in nano-structured magnets. The results of the present study are summarized as follows ;1)By using a new domain wall resonance spectroscopy, the mass of a magnetic wall in a semi-circle nano-line is determined to be 6.6x10-23 kg, the value of which is well in agreement with that predicted by V. W. Doring in 1948. It is shown that the domain wall is driven by low AC current density which enables negligible small Joule heating.2)The magnetic structure and magnetization process in a Permalloy wire-based honeycomb network have been investigated by means of MFM and magnetoresistance. It is found that the magnetic structure is governed by magnetic interaction similar to the ice rule. By decreasing the exchange energy at the vertices of the network, the ice-rule type of interaction causes a transition of the magnetization process.3)Magnetoresistance for tri-layered Py/Cu/Py nanoring is measured. The ring detects the electron coherence modulated by the inhomogeneous magnetization distribution.4)The magnetoresistance effect and the current-voltage characteristics in ballistic nano-contacts in the regime of conductance quantization are investigated. The spin arrangement in the contacts plays an important role for quantum conductance.5)The inverse process of the spin-Hall effect is observed at room temperature in a Py/Pt thin film by the ferromagnetic resonance of Py film.6)The conduction of a single ferromagnetic nanowire in a radio frequency range is investigated and the magnetic field and frequency dependences of the spin torque diode effect are clarified.