Papers by Keyword: Magnetic Interaction

Abstract: In recent years, utilizing kinetic energy in mechanical vibrations has become an interesting area of research. This is due to ubiquitous sources of vibration energy, coupled with the ever increasing demands to power wireless sensing electronics and Microelectromechanical (MEMs) devices with low energy requirements. Thus, researchers have ventured into developing different system configurations with the aim of harvesting vibration energy to power these devices. Cantilever beam systems with piezoelectric layer have been used as vibration energy scavengers due to their abilities of converting kinetic energy in vibrating bodies into electrical energy, whereas permanent magnets have been used to improve their performance. The only unresolved challenge is to develop energy harvesters that can produce optimum energy at a wider bandwidth. In this study, a mathematical model of a system of cantilever beams with piezoelectric layers having a magnetic coupled tip mass is proposed. The lumped parameter model of the harvester is developed to estimate the power output of the proposed harvester, and to visualise the effect of magnetic coupled tip mass in widening the frequency bandwidth of the energy harvester. Preliminary Simulation results using MATLAB have however shown the effectiveness of the proposed system.

Abstract: Mixed-metal cyano-bridged compounds Gu_nM_1.5-n[Fe (CN)₆]·xH₂O(M=Ni, Gu) have been prepared by co-precipitation. The magnetic results show that the compound Cu_0.75Ni_0.75[Fe (CN)₆]·xH₂O is ferromagnetic, undergoes a paramagnetic to the ferromagnetic transition temperature at 21.77 K. The paramagnetic curie temperature θ, residual magnetization M_r, and coercive field H_c are different from bimetallic Prussian Blue analogues Ni₃[Fe (CN)₆]₂·xH₂O and Cu₃[Fe (CN)₆]₂· xH₂O. As to Cu₃[Fe (CN)₆]₂·xH₂O, the magnetic susceptibilities follow the Curie-Weiss law and the Weiss paramagnetic Curie temperature is 19.1 K. The Mossbauer spectrum at room temperature reveals a doublet with the isomer shift parameter (-0.03 mm/s) and quadrupole splitting (QS= 1.09 mm/s). As the sample was cooled down to 16K, the magnetic splitting phenomenon was detected in the compound.

Abstract: The cyano-bridged complex Co [Fe (CN)₅NO]·5H₂O has been synthesized. According to the reaction of cyanide-based unsaturated ligand precursor (molecular fragments)[BL_y(CN)_x]^n-with the metal ions or complex unsaturated ligand, it is easy to control the structure of molecular magnets and tune up the magnetic properties. Hetero binuclear complex Co [Fe (CN)₅NO]∙5H₂O was prepared through [Fe (CN)₅NO]^2- ion. The room temperature Mossbauer spectrum revealed a doublet with the isomer shift parameter (-0.44(7) mm/s) and quadrupole splitting (QS = 1.91(3) mm / s) characteristic for low-spin Fe (III) ions. The low-spin (S = 1/2) of the Fe (III) ion of valence electrons on the electric field gradient (EFG) was caused by non-zero contribution. DC and AC magnetic measurements showed that the complexes belonged to the anti-ferromagnetic material, with a magnetic phase transition temperature below 2K.

Abstract: In this article is presented a dynamic mathematical model for a new type of dynamic balancing system, having a driving solution of the rotating part based on magnetic interactions. Experimental studies for evaluation of the dynamic stiffness and damping due to the magnetic coupling were performed by measuring the radial mobility of the whole system. The experimental studies were used to improve the analytical model.

Abstract: The mixed valency character and antiferromagnetic coupling in Molecule magnets Materials NBu4FeIInMnII1-n[FeIII(OX)3]（n=0.03、0.10、0.15、0.97） were investigated by magnetic measurements.The values of M increase and exhibit weak irreversibility in the field-cooled (FC) magnetization curves. There are a clear bifurcation phenomenon of the field-cooled (MFC) and Zero-field-cooled (MZFC) magnetization curves.In the Molecule magnets Materials NBu4FeII0.10 MnII0.90[FeIII(OX)3],the Ne´el temperature is 34 K.And the Ne´el temperature of NBu4FeII0.15MnII0.85 [FeIII(OX)3] is 28 K.In the sample NBu4FeII0.03 MnII0.97[FeIII(OX)3],,the bifurcation of the ZFC and FC plots below the Ne´el temperature of 30 K indicates irreversibility.The oxalate group has been shown to be an excellent bridging ligand in supporting the magnetic exchange interaction.

Abstract: The cyano-bridged complexe [Gu(en)x]yMA[Fe(CN)6]z·nH2O(MA=K+) have been synthesized. In the compound [Cu(en)2][KFe(CN)6]·H2O, we shows firstly a weak intramolecular anti-ferromagnetic coupling between Fe3+(ground state 5T2g, S=1/2) and Cu2+(ground state 6T2g3eg, S=1/2) through the long- range cyano bridges. The magnetic susceptibility obey the curie-weiss law [χ=C/(T-θ)] with a negative weiss constant,the curie constant C=0.42cm3·k·mol-1, the compound exists a strong Cu2+–CN–Fe3+ ferromagnetic interaction and a weak Cu2+(ground state 6T2g3eg, S=1/2)–Cu2+(ground state 6T2g3eg, S=1/2) antiferromagnetic interaction, through long range of NC-Fe-CN. At the same time, we have given an explanation from magnetic properties and struction of compounds.

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: Magnetic fluid is a stable colloidal dispersion of ferromagnetic particles in a liquid carrier. Once a magnetic field is applied to magnetic fluids (MF), various structures of MF are formed. A detailed understanding of structures and particle distributions in gradient magnetic fields is much important. But very few works have been done on this. In the present study, the effects of magnetic field gradient and magnetic interaction among magnetic particles on the structures of MF are investigated using a two-dimensional Monte Carlo simulation. The results show that a gradient distribution of magnetic particles is formed under gradient magnetic fields. However, as the interaction between magnetic particles increases, the distribution gradient decreases, accompanied by the formation of chain-like clusters. Moreover, with increasing the magnetic interaction, particle distribution changes from grass-like clusters to needle-like ones.