Xiaobin Luo

Capacitive type magnetoimpedance effect in piezoelectric-magnetostrictive composite resonator

In this article, a significant capacitive type magnetoimpedance effect of piezoelectric-magnetostrictive (PM) composite resonator is presented at room temperature. The variations of relatively effective permittivity of the PM resonator with a dc magnetic field are responsible for the capacitive type magnetoimpedance effect. About 225% and 50% of magnetoimpedance have been achieved at anti-resonance and resonance frequencies of the PM resonator, respectively, which reveals a stronger magnetoelectric coupling at the anti-resonance frequency than that at the resonance frequency of the PM resonator. A detailed analysis also indicates that the magnetocapacitance and magnetoinduction effects of the resonator were originated from the variations of relatively effective permittivity of the resonator. More than 200% and 170% of magnetocapacitance and magnetoinduction were achieved at room temperature in the anti-resonance window, respectively, and also about 150% and 60% of capacitance and induction modulation were observed in the resonance window by applying the dc magnetic fields. The capacitive type magnetoimpedance effect is expected to be used in the design of magnetic-field-tuned ultrasonic transducer.

Electrostrain-controlled displacement-permeability in composite of ferroelectrics and heterotypic complex ferrite

By using the product effects of electrostrain and displacement-permeability, a composite containing a bar of Pb(Zr,Ti)O3 and two I-shaped ferrites were developed, and its electromagnetic effect was investigated. Under a constant electric field of 5 kV/cm, about 36% of the electric field-controlled permeability and impedance were observed in a considerably wide scope of frequency. The electric-field dependent inductance and impedance of the composite device showed a ferroelectric relaxation behavior. Analysis showed that the degenerating field-dependent permeability was responsible for the electromagnetic effects observed.

The Effect of Magnetic Field-Tuned Resonance on the Capacitance of Laminate Composites

The magneto-electric coupling and magneto-capacitance effect of a layer composite ferromagnet/ piezoelectric/ferromagnet was investigated. Several resonant peaks were observed on the curves of the capacitance versus frequency. The resonant peaks were found to shift under an applied magnetic field, and the impedance of the sample can be changed from capacitive to inductive ones with changing the field. Thus, giant negative and positive magneto-capacitance effects can be observed simultaneously under a magnetic field less than 1 k Oe near the resonant points. Experimental and theoretical analysis showed that such magnetically tuned variation in impedance originates from the magnetic field-induced change of the compliances of the magnetic phase of the composite.

Magneto-Birefringence in Layered Composites at Room-Temperature

By the product of magnetostriction and stress-birefringence, the laminate composites that can show Voigt effect was suggested and fabricated. Under a magnetic field no stronger than 1900 Oe, a phase difference of about 3.3 was observed for a trilayer composite Tb1-xDyxFe2-y / polycarbonate / Tb1-xDyxFe2-y with the polycarbonate layer in size of 5×2.75×20 mm3 at room temperature, resulting in a half-wave magnetic field of no greater than 270 Oe.