Papers by Keyword: Spin

Abstract: In the summer school of PSD2024, focusing on spin-polarized positron annihilation spectroscopy in materials science, I reported the historical background and its possibility concerning current spintronics field, the basic principles, and prospects. Here, as a memorandum, I mainly summarize the basic principles, which can be relatively well-formulated, with some remarks.

Abstract: We briefly review the spin-polarized positron annihilation experiments on some ferromagnets (Fe, Co, Ni, Gd, Co₂MnSi, Co₂MnAl and NiMnSb) using positron beams generated with ⁶⁸Ge-⁶⁸Ga sources. The differential DBAR spectra between majority and minority spin electrons are well interpreted by the first principles band structure calculation. This further provides information about the half-metallicity of the Heusler alloys. The surfaces of Fe, Co and Ni are more negatively spin-polarized, that is, there are more majority than minority spin electrons. To explain the observed spin polarization quantitatively, detailed theoretical calculations and further experiments are required.

Abstract: Study the magnetic properties of Si<B,Ni> whiskers, the concentration of which corresponds to a dielectric and metal side of metal-insulator transition, is performed. Percolation laws of the magnetic clusters formation, that is important for development of spintronic devices, are considered.

Abstract: The atomic spin interaction is very important for understanding the superficially magnetic feature of nanostructure at atomic level. Magnetic exchange force microscopy (MExFM) is an innovative means of measuring surface spin force. But it is difficult to separate the surface topography and spin information. We develop the magnetic exchange force microscopy using ferromagnetic resonance (FMR-MExFM). The theoretical and experimental results demonstrate that this method can separate the two kinds of information effectively. Here, in order to obtain the high sensitivity in detecting the ferromagnetic resonance, we fabricate the microwave irradiation device to optimize the position between the device and the cantilever. We have succeeded in observing the ferromagnetic resonance effect and determining its resonant frequency using the homemade microwave irradiation device and the network analyzer. This research is very important for developing FMR-MExFM and novel magnetic sensor, detecting the magnetic information, etc.

Abstract: We tried to combine the basic principle of grammatical evolution with vortex-ring-fractal structures of atoms to create new molecule structures. This approach combines knowledge of evolutionary optimization with physical chemistry.

Abstract: Wireless Sensor Network (WSN) is a network which connect the human and the nature. The lifetime is an important standard which measures the network is good or not. The routing can influence on the lifetime of the network. This paper mainly introduces some routing protocols in WSN and describes their advantages and shortcomings.

Abstract: In recent decades, a new magnetic sensor based on magnetoresistance effect is highly researched and developed intensively. GMR material has great potential as next generation magnetic field sensing devices. It has also good magnetic and electric properties, and high potential to be developed into various applications of electronic devices such as: magnetic field sensor, current measurements, linear and rotational position sensor, data storage, head recording, and non-volatile magnetic random access memory. GMR material can be developed to be solid state magnetic sensors that are widely used in low field magnetic sensing applications. A solid state magnetic sensor can directly convert magnetic field into resistance, which can be easily detected by applying a sense current or voltage. Generally, there are many sensors for measuring the low magnetic field, such as: fluxgate sensor, Hall sensor, induction coil, GMR sensor, and SQUID sensor. Compared to other low magnetic field sensing techniques, solid state sensors have demonstrated many advantages, such as: small size (<0.1mm²), low power, high sensitivity (~0.1Oe) and good compatibility with CMOS technology. The thin film of GMR is usually prepared using: sputtering, electro deposition or molecular beam epitaxy (MBE) techniques. But so far, not many researchers reported the manufacture of thin film of GMR by dc-Opposed Target Magnetron Sputtering (dc-OTMS). In this paper, we inform the development of GMR thin film with sandwich and spin valve structures using dc-OTMS method. We have also developed organic GMR with Alq3 as a spacer layer.

Abstract: The cyano-bridged complexes [MA(en)x]y[Fe(CN)6]z·nH2O(MA=Co2+、Gu2+) have been synthesized. In the multi-metal compound [Co(en)3] [Fe(CN)6] ·6.1H2O was prepared. Infrared spectra with stretching vibration CN = 2117.27 cm-1 illustrates that there exists the bridged cyanide on the compound; the Curie temperature Ө is -8.23117 K, indicating the magnetic interaction between the metal ions in the compound is very weak.In the multi-metal compound CuII3[FeIII(CN)6]2·3NH3·6H2O, we shows firstly the coexistence of ferromagnetic order and spin-glass order.The irreversibility in the MFC/MZFC and the relaxation of MZFC suggest that the magnetic system can be visualized as containing a ferromagnetic cluster of spin below Tc, mixed with small spin-glass clusters formed below temperature Tg less than Tc. The observed magnetic properties are explained with a ferromagnetic-spin-glass phase model.

Abstract: Torsion experiments should be adopted to characterize large strain elasto-plastic behavior of material instead of traditional uni-axial tension experiments due to the plastic stability of specimen in torsion deformation. Study on spins and deformation rate in finite torsion deformation is the key to determine the material parameters by torsion experiments and understand the finite deformation characteristics of material. In this paper, five spins and deformation rate in torsion deformation with solid circular shafts are investigated in cylinder coordinates. The expressions of the deformation rate and spins, namely the material spin, the relative spin, the spin of the frame of the deformation rate, logarithmic spin and instantaneous spin considering the effect of stress, are deduced by analyzing the finite torsion deformation. The comparisons are made among all spins obtained in this paper. The results obtained in this paper are the basis of analyzing the large strain constitutive relationship based on torsion experiments with solid circular shafts.

Abstract: Dipositronium, Ps2, was recently prepared [1]. This is significant because: • It is the first laboratory observation of a molecule that contains more than one positron; • It is the most symmetrical molecule possible; • It is the most non-rigid (floppiest) molecule possible; • The interval between the theoretical establishment of its existence [2] and its laboratory observation [1] is inordinately long – 60 years; and • An extension of the technology developed for the Ps2 observation may soon lead to an observation of the Bose-Einstein condensation of positronium and the development of a gamma ray laser. We briefly discuss the symmetry of Ps2 and how an understanding of it will underlie its characterization in the future. Ps2O and CPs2 might be the next two-positron compounds to be prepared and characterized in the laboratory. A discussion of the contrasting eigenstates of these two molecules is given. An understanding of these states is required in order to identify them.