Jun Ou-Yang

Ferromagnetic resonance induced large microwave magnetodielectric effect in cerium doped Y 3 Fe 5 O 12 ferrites

In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3−xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4–8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to −5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodielectric effect in YIG ferrites is of great importance to the development of next generation multifunctional adaptive microwave materials, devices and integrated circuits.

Electric field control of exchange-spring behavior

We study the electric field control of exchange-spring (ES) behavior in a piezoelectric/ES multi-layer using the micromagnetic simulation method. In the composite, PZT or PZN-PT forms the piezoelectric substrate, while the ES bilayer is composed of hard-magnetic (HM) CoFe2O4 (CFO) and soft-magnetic (SM) Fe3O4 or Co43Fe43B14 materials. The stress as a function of electric-field strength (E) and the external magnetic field was set to align in plane. The results reveal an E-sensitive magnetic property in the PZN-PT/Co43Fe43B14/CFO system. The ES bilayer in this system experienced a transition from rigid magnetism to ES behavior with E changing from 2 MV/m to −2 MV/m. The E-related nucleation field and switching field exhibit strong dependences on the thickness ratio between the HM and SM phases. Additionally, when the magnetic field was applied at an acute angle to the easy axis of the HM or the SM phase, a multi-jump hysteresis loop was observed under a negative E bias. These results may be attributed to a ...

Magnetoelectric response of AlN/[(Fe90Co10)78Si12B10 + Terfenol-D] composite films

The magnetoelectric (ME) composite films composed of piezoelectric layer AlN film and new magnetostrictive layer [(Fe90Co10)78Si12B10 + Terfenol-D] films were successfully prepared by RF magnetron sputtering. The influence of bias magnetic field Hdc on ME response, as well as, the ac magnetic field sensitivity were investigated in detail. The results demonstrated that the respective magnetic properties of (Fe90Co10)78Si12B10 and Terfenol-D films are coupled in this new magnetostrictive layer, resulting in the fact that ME voltage coefficient αME reaches the maximum of 78.1 V/cm Oe and 77.5 V/cm Oe at the bias field of 11 Oe and 96 Oe, respectively. Meanwhile, the composite films display ac magnetic field sensitivity of 0.45 nT/√Hz and 0.47 nT/√Hz at Hdc of 11 Oe and 96 Oe, respectively. The results above indicate that the AlN/[(Fe90Co10)78Si12B10 + Terfenol-D] composite films exhibit a promising potential application in diverse range of magnetic field detection.

Significant manipulation of output performance of a bridge-structured spin valve magnetoresistance sensor via an electric field

Through principles of spin-valve giant magnetoresistance (SV-GMR) effect and its application in magnetic sensors, we have investigated electric-field control of the output performance of a bridge-structured Co/Cu/NiFe/IrMn SV-GMR sensor on a PZN-PT piezoelectric substrate using the micro-magnetic simulation. We centered on the influence of the variation of uniaxial magnetic anisotropy constant (K) of Co on the output of the bridge, and K was manipulated via the stress of Co, which is generated from the strain of a piezoelectric substrate under an electric field. The results indicate that when K varies between 2 × 104 J/m3 and 10 × 104 J/m3, the output performance can be significantly manipulated: The linear range alters from between −330 Oe and 330 Oe to between −650 Oe and 650 Oe, and the sensitivity is tuned by almost 7 times, making it possible to measure magnetic fields with very different ranges. According to the converse piezoelectric effect, we have found that this variation of K can be realized by...

Electric field induced non-90° rotation of the easy axis of a ferromagnetic film

We report that an electric field can induce a non-90° rotation of an in-plane easy axis of a magnetic thin film. Based on the magnetic hysteresis loop measurements for a FeCoSiB/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 multiferroic heterostructure, we found that when an electric field induced uniaxial anisotropy field HK1 is generated in a magnetic film with an initial uniaxial anisotropy field HK2, and there is a non-90° angle between these fields, the combination of these two fields effectively rotates HK2 by a non-90° angle. Based on the measurement of anisotropic magnetoresistance, one can see that the non-90° rotation of the easy axis changes the direction of the magnetic field for observing the maximum and minimum magnetoresistance. The mechanism for this non-90° rotation of the easy axis was discussed using the theory of magnetic anisotropy. This research paves a way for the development of magnetic sensors with an ability to control the direction of the measured magnetic field by using an external electric field.

Transferred PMN-PT Thick Film on Conductive Silver Epoxy

Approximately 25 μm Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) thick film was synthesized based on a sol-gel/composite route. The obtained PMN-PT thick film was successfully transferred from the Silicon substrate to the conductive silver epoxy using a novel wet chemical method. The mechanism of this damage free transfer was explored and analyzed. Compared with the film on Silicon substrate, the transferred one exhibited superior dielectric, ferroelectric and piezoelectric properties. These promising results indicate that transferred PMN-PT thick film possesses the capability for piezoelectric device application, especially for ultrasound transducer fabrication. Most importantly, this chemical route opens a new path for transfer of thick film.

Giant Magneto-Impedance (GMI) Effect in Single-Layer Soft Magnetic Film Under Stress

The stress-induced magnetic anisotropy can significantly affect giant magneto-impedance (GMI) effect of the soft magnetic film. This paper is devoted to the GMI effect of the single layer soft magnetic film implied without and with a stress. By simulating a physical model with MATLAB and COMSOL software, the impedance expression of the single layer soft magnetic film and the relation between external magnetic field and magnetic permeability are deduced. We observed that, without a stress, the sensitive region increased firstly and then decreased with the increasing of the excitation current frequency from 1 MHz to 200 MHz. While the film was subjected to the stress in the direction of the current with one end stressed, the stress on the film was gradually reduced from stressed end to free end. Also, the impedance change rate of the film changed when the stress was added, which is similar to the effect of adding a bias magnetic field on the film. More importantly, the addition of stress σ can induce the bias of the GMI measurement range and improve its sensitivity near zero magnetic fields. This may provide a new way for designing a GMI sensor with higher sensitivity and adjustable measurement range.

Self-biased vector magnetic sensor based on a Love-type surface acoustic wave resonator

Magnetic sensors based on the interaction between the delta-E effect and surface acoustic waves (SAWs) are promising devices due to their simple driving circuits. In this study, a magnetic sensor composed of a (Fe90Co10)78Si12B10 magnetic layer and Love-type SAW resonator was investigated. The resonance frequency sensitivities (RFS) of the sensor resulting from the delta-E effect are 76.06 Hz/μT and 364.28 Hz/μT in the L-direction (along the easy axis) and W-direction (along the hard axis), respectively. The maximum RFS achieved by this magnetic sensor is 663.98 Hz/μT along the hard axis, with a resonance frequency of 221.76 MHz. The shift of resonance frequency shows a good linearity along with the external magnetic field in the L-direction. The curves of frequency response demonstrate point symmetry rather than the expected axial symmetry in both directions, due to the existence of residual magnetization. Non-zero RFS at zero magnetic field also appears in this device, because of the non-zero change of the Youngs modulus at zero magnetic field. The good linearity and high sensitivity mean that the investigated magnetic sensor can be applied for weak DC magnetic field detection.Magnetic sensors based on the interaction between the delta-E effect and surface acoustic waves (SAWs) are promising devices due to their simple driving circuits. In this study, a magnetic sensor composed of a (Fe90Co10)78Si12B10 magnetic layer and Love-type SAW resonator was investigated. The resonance frequency sensitivities (RFS) of the sensor resulting from the delta-E effect are 76.06 Hz/μT and 364.28 Hz/μT in the L-direction (along the easy axis) and W-direction (along the hard axis), respectively. The maximum RFS achieved by this magnetic sensor is 663.98 Hz/μT along the hard axis, with a resonance frequency of 221.76 MHz. The shift of resonance frequency shows a good linearity along with the external magnetic field in the L-direction. The curves of frequency response demonstrate point symmetry rather than the expected axial symmetry in both directions, due to the existence of residual magnetization. Non-zero RFS at zero magnetic field also appears in this device, because of the non-zero change of ...

Motion of a skyrmionium driven by spin wave

A skyrmionium is composed of two skyrmions with opposite skyrmion numbers and different sizes in the same track. In recent years, the motion of a skyrmionium driven by spin-polarized current has been investigated. However, the motion of a skyrmionium driven by a spin wave has not been reported. In this paper, we report our work concerning the numerical analysis of spin wave-driven motion of a skyrmionium in a nanotrack. The results show that the motion of a skyrmionium was significantly influenced by varying the frequency and amplitude of the AC magnetic field for exciting a spin wave, the distance between the spin wave source and the skyrmionium, the damping coefficient of the ferromagnetic track, and the track width. We found skyrmionium deformation during its initial motion process, but its shape could be recovered as it moved farther away from the spin wave source. Additionally, a series of velocity peaks were observed in the frequency range between 25 GHz and 175 GHz. When compared to a skyrmion, the...

Simulation of stress effect on GMI in soft magnetic amorphous film

Soft magnetic amorphous film not only has the giant magneto-impedance (GMI) effect, but also significantly affected by stress-induced magnetic anisotropy[1].