No abstract

No abstract

Spin excitations of the magnetic vortex state in ferromagnetic nanodots are measured using Brillouin light scattering. Arrays of permalloy dots with 800-nm diameter and 60-nm thickness were fabricated by means of electron beam lithography and lift-off procedures. Two excitation modes are observed experimentally in the vortex state. One mode, at ϳ12 GHz, decreases slightly in frequency to 11 GHz as an in-plane magnetic field is applied. The lower mode, at ϳ8 GHz, is almost independent of applied field strength. Numerical and analytical calculations of the dynamic magnetization based on the Landau-Lifshitz equation of motion allows us to identify the higher and lower frequency modes as corresponding to dipole-dominated spin excitations localized inside the dot and at the dot edges, respectively.

The evolution of a magnetic “vortex” state in submicron ferromagnetic disks has been studied as functions of disk diameter and thickness. The vortex core displacement in the applied magnetic field was calculated by minimizing the total magnetic energy consisting of the magnetostatic, exchange, and Zeeman energies. A simple analytical expression for the initial magnetic susceptibility is deduced. The initial susceptibility increases with increasing disk diameter and decreasing thickness. The calculations agree well with the experimental data obtained for the 60 nm thick permalloy disk arrays with a variable diameter from 0.2 to 0.8 μm.

No abstract

We here demonstrate the interfacial spin to charge current conversion by means of spin pumping from a ferromagnetic Permalloy (Py: Ni 80 Fe 20 ) to a Cu/Bi 2 O 3 interface. A clear signature of the spin to charge current conversion was observed in voltage spectrum of a Py/Cu/Bi 2 O 3 trilayer film whereas no signature in a Py/Cu and Py/Bi 2 O 3 bilayer films. We also found that the conversion coefficient strongly depended on Cu thickness, reflecting the thickness dependent momentum relaxation time in Cu layer.

Click beetle luciferase (CBLuc) is insensitive to pH, temperature, and heavy metals, and emits a stable, highly tissue-transparent red light with luciferin in physiological circumstances. Thus, the luminescence signal is optimal for a bioanalytical index reporting the magnitude of a signal transduction of interest. Here, we validated a single-molecule-format complementation system of split CBLuc to study signal-controlled protein-protein (peptide) interactions. First, we generated 10 pairs of N- and C-terminal fragments of CBLuc to examine respectively whether a significant recovery of the activity occurs through the intramolecular complementation. The ligand binding domain of androgen receptor (AR LBD) was connected to a functional peptide sequence through a flexible linker. The fusion protein was then sandwiched between the dissected N- and C-terminal fragments of CBLuc. Androgen induces the association between AR LBD and a functional peptide and the subsequent complementation of N- and C-terminal fragments of split CBLuc inside the single-molecule-format probe, which restores the activities of CBLuc. The examination about the dissection sites of CBLuc revealed that the dissection positions next to the amino acids D412 and I439 admit a stable recovery of CBLuc activity through an intramolecular complementation. The ligand sensitivity and kinetics of the single molecular probe with split CBLuc were discussed in various cell lines and in different protein-peptide binding models. The probe is applicable to developing biotherapeutic agents on the AR signaling and for screening adverse chemicals that possibly influence the signal transduction of proteins in living cells or animals.

Spin-flip mechanism in Ag nanowires with MgO surface protection layers has been investigated by means of nonlocal spin valve measurements using Permalloy/Ag lateral spin valves. The spin flip events mediated by surface scattering are effectively suppressed by the MgO capping layer. The spin relaxation process was found to be well described in the framework of Elliott-Yafet mechanism and then the probabilities of spin-filp scattering for phonon or impurity mediated momentum scattering is precisely determined in the nanowires. The temperature dependent spin-lattice relaxation follows the Bloch-Grüneisen theory and falls on to a universal curve for the monovalent metals as in the Monod and Beuneu scaling determined from the conduction electron spin resonance data for bulk.Spin injection, transport and detection are key ingredients in spintoronics, which have drawn a great deal of attention in recent years due to possible application for magnetic memories as well as fundamental interests concerning the interplay between charge and spin transport. 1,2 Lateral spin valves (LSVs) offer an effective means to study transport properties of a pure spin current, i.e., a diffusive flow of spin angular momentum accompanying no charge currents. A large number of the spin injection experiments have been reported since the pioneering work by Johnson and Silsbee in 1985. 3 More recently non-local spin valve experiments by Jedema et al. 4 brought renewed interests in LSVs in response to the timely development in both micro-fabrication technology and emergent interest in the pure spin current. Having a betterinsight into the spin transport and relaxation mechanism in nano-scaled devices is important to enhance the performance for the spintronic application.The spin relaxation mechanism in nonmagnetic metals (NM) has originally been discussed by Elliott and Yafet. 5,6 According to their theory, the spin-orbit interaction (SOI) in NM lifts the spin degeneracy of Bloch electrons, and results in two different energy states for up or down spin.The spin relaxation, i.e., the transition between the opposite spin states, can therefore be caused by the spin independent momentum scatterings due to impurities, grain boundaries, surfaces and phonon. [5][6][7] The earlier experimental works on the spin relaxation mechanism were mainly performed by conduction electron spin resonance (CESR) measurements and the results were