Lezhong Li

Synthesis of TbCu7-type Structural SmCo-based Films for Microelectromechanical System Applications

Abstract Development of microelectromechanical system (MEMS) requires permanent magnetic films prepared on Si substrates with good thermal stability. The SmCo-based films were deposited on Si (100) substrates by magnetron sputtering process, and the effect of sputtering parameters on deposition rate, microstructure, crystal structure, and magnetic properties were investigated subsequently. The results show that the TbCu7-type structural SmCo-based film is obtained with adjusted sputtering parameters. The film exhibits a well preferred crystal orientation and fine microstructure, leading to better in-plane magnetic properties and a magnetization reversal process mainly controlled by domain wall pinning mechanism.

Structural, magnetic and electrical properties in Al-substitued NiZnCo ferrite prepared via the sol–gel auto-combustion method for LTCC technology

Al-substituted NiZnCo ferrite, Ni0.4Zn0.5Co0.1AlxFe2−xO4 (0 ≤ x ≤ 0.20), were synthesized by the sol–gel auto-combustion method. The effects of Al substitution on the structural, magnetic and electrical properties have been investigated. The X-ray diffraction patterns show that the lattice parameter decreases with the increase of Al substitution. The SEM images show that the grain size decreases with the increase of Al substitution. The initial magnetic permeability reaches the maximum value when Al substitution is 0.05. The resonance frequency is inversely proportional to initial magnetic permeability which obeys Snoeks law. The temperature coefficient reaches the maximum value when Al substitution is 0.05, and it has the minimum value when Al substitution is 0.20. The Curie temperature decreases with the increase of Al temperature due to the number of nonmagnetic Al3+ ions increase results in the decrease of superexchange interaction. The saturation magnetization and coercivity of the ferrite decrease linearly with the increase of Al substitution. The real dielectric constant of Ni0.4Zn0.5Co0.1AlxFe2−xO4 ferrite decreases exponentially as frequency increases, and the dielectric constants decrease with the increase of Al substitution. The direct-current resistivity decreases and follows an exponential decay with the increase of temperature, and it increases with Al substitution.

The high-pressure structural transition in MnS: an ab initio study

The structural phase transition between B1 (α-MnS) and B3 (β-MnS) is investigated using a density functional theory method. The structural phase transition pressure Pt from α-MnS to β-MnS, which is determined on the basis of the third-order Birch–Murnaghan equation of states, is 30.75 GPa. Also, the lattice parameters a, the bulk modulus B and pressure derivative of bulk modulus B′, which are generally in good agreement with experiments and other theoretical values, are obtained under zero pressure. For further investigation of the structural phase transition pressure of MnS, the relative volumes V/V 0, the bulk modulus B, first and second pressure derivatives (B′ and B″) of bulk modulus for the two structures of MnS have been calculated under various pressures.

Diagnosis of Coupled Resonator Bandpass Filters Using VF and Optimization Method

This paper presents a hybrid method combining a vector fitting (VF) and a global optimization for diagnosing coupled resonator bandpass filters. The method can extract coupling matrix from the measured or electromagnetically simulated admittance parameters (Y -parameters) of a narrow band coupled resonator bandpass filter with losses. The optimization method is used to remove the phase shift effects of the measured or the EM simulated Y -parameters caused by the loaded transmission lines at the input/output ports of a filter. VF is applied to determine the complex poles and residues of the Y -parameters without phase shift. The coupling matrix can be extracted (also called the filter diagnosis) by these complex poles and residues. The method can be used to computer-aided tuning (CAT) of a filter in the stage of this filter design and/or product process to accelerate its physical design. Three application examples illustrate the validity of the proposed method.