Magnetic sensitivity technology based on microwave modulation of solid state spin system NV center

In view of the low resolution and accuracy of traditional magnetometer,a method of microwave frequency modulation technology based on nitrogen-vacancy(NV)center in diamond for magnetic detection was proposed.The magnetometer studied can reduce the frequency noise of system and improve the magnetic sensitivity by microwave frequency modulation.Firstly,ESR spectra by sweeping the microwave frequency was obtained.Further,the microwave frequency modulated was gained through the mixed high-frequency sinusoidal modulation signal generated by signal generator.In addition,the frequency through the lock-in amplifier was locked,and the signal which was proportional to the first derivative of the spectrum was obtained.The experimental results show that the sensitivity of magnetic field detection can reach 17.628 nT/Hz based on microwave frequency modulation technology.The method realizes high resolution and sensitivity for magnetic field detection.

Investigation on interface of NiFeCr/NiFe/Ta films with high magnetic field sensitivity

NiFeCr/NiFe/Ta films with excellent performance were prepared by magnetron sputtering system.The anisotropic magetoresistance (AMR) value (ΔR/R) and magnetic filed sensitivity (Sv,Sv=[d(ΔR/R)/dH]max.) for the 12 nm NiFe film deposited on NiFeCr buffer layer were 3.66% and 1.42×10-4%·T-1,respectively.The higher Sv of the film is close to that of a spin valve (SV).The microstructure analysis shows that the NiFeCr buffer layer has adopted the same structure with the same interplanar distance as the NiFe layer,inducing a strong NiFe (111) texture,and that the NiFeCr/NiFe interface is quite smooth,leading to a high degree of specular reflection of conduction electrons.Both increase the ΔR and reduce the R in the film,which lead to the high ΔR/R.Clean substrate surfaces are critical for preparation of high performance NiFeCr/NiFe/Ta films,and sputter cleaning or pre-deposition of 5 nm amorphous Al2O3 layer in the deposition chamber can provide the re-quired clean substrate surfaces for the growth of the buffer layer.

Haptic Interface with Magnetic Field Sensitive Elastomer

Sense of touch is one of the important information from environment for human to live in daily life. Haptic interface is a hot topic in virtual reality but almost all of the devices focus on fingers and hands as targets. In this paper, we focus on the foot haptic device with magnetic flied sensitive elastomer （MSE）. We developed a haptic unit used as a magnetic field generator for MSE and contact point of foot haptic device. MSE samples mixed with 80 wt% carbonyl iron particles were prepared and evaluated with the developed magnet. Experimental results show that the mechanical property of the haptic unit can be modeled with the adjustable friction element. This property has a good advantage for the haptic unit.

Highly Sensitive Fiber-Optic Faraday-Effect Magnetic Field Sensor Based on Yttrium Iron Garnet

The principle and performance of a fiber-optic Faraday-effect magnetic-field sensor based on an yttrium iron garnet (YIG) and two flux concentrations are described. A single polarization-maintaining optical fiber links the sensor head to the source and detection system, in which the technique of phase shift cancellation is used to cancel the phase shift that accumulatein the optical fiber. Flux concentrators were exploited to enhance the YIG crystal magneto-optic sensitivity .The sensor system exhibited a noise-equivalent field of 8 pT/√Hz and a 3 dB bandwidth of ～10 MHz.

Fabrication and characteristics of magnetic field sensors based on nano-polysilicon thin-film transistors

A magnetic field sensor based on nano-polysilicon thin films transistors(TFTs) with Hall probes is proposed.The magnetic field sensors are fabricated on <100> orientation high resistivity(ρ>500Ω·cm) silicon substrates by using CMOS technology,which adopt nano-polysilicon thin films with thicknesses of 90 nm and heterojunction interfaces between the nano-polysilicon thin films and the high resistivity silicon substrates as the sensing layers.The experimental results show that when V_(DS) = 5.0 V,the magnetic sensitivities of magnetic field sensors based on nano-polysilicon TFTs with length-width ratios of 160μm/80μm,320μm/80μm and 480μm/80μm are 78 mV/T,55 mV/T and 34 mV/T,respectively.Under the same conditions,the magnetic sensitivity of the obtained magnetic field sensor is significantly improved in comparison with a Hall magnetic field sensor adopting silicon as the sensing layers.

Fiber structures and material science in optical fiber magnetic field sensors

Magnetic feld sensing plays an important role in many felds of scientifc research and engineering applications.Benefting from the advantages of optical fbers,the optical fber-based magnetic feld sensors demonstrate characteristics of light weight,small size,remote controllability,reliable security,and wide dynamic ranges.This paper provides an overview of the basic principles,development,and applications of optical fber magnetic feld sensors.The sensing mechanisms of fber grating,interferometric and evanescent feld fber are discussed in detail.Magnetic fuid materials,magneto-strictive materials,and magneto-optical materials used in optical fber sensing systems are also introduced.The applications of optical fber magnetic feld sensors as current sensors,geomagnetic monitoring,and quasi-distributed magnetic sensors are presented.In addition,challenges and future development directions are analyzed.

Natural Convection of Temperature-Sensitive Magnetic Fluids in Porous Media

In this article,natural convection of a temperature-sensitive magnetic fluid in a porous media is studied numerically by using lattice Boltzmann method.Results show that the heat transfer decreases when the ball numbers increase.When the magnetic field is increased,the heat transfer is enhanced;however the average wall Nusselt number increases at small ball numbers but decreases at large ball numbers due to the induced flow being more likely confined near the bottom walls with a high number of obstacles.

Fabrication and characteristics of the nc-Si/c-Si heterojunction MAGFET

A MAGFET using an nc-Si/c-Si heterojunction as source and drain was fabricated by CMOS technology, using two ohm-contact electrodes as Hall outputs on double sides of the channel situated 0.7L from the source. The experimental results show that when VDS = -7.0 V, the magnetic sensitivity of the single nc-Si/c-Si heterojunction magnetic metal oxide semiconductor field effect transistor （MAGFET） with an L ： W ratio of 2 ： 1 is 21.26 mV/T, and that with an L ： W ratio of 4 ： 1 is 13.88 mV/T. When the outputs of double nc-Si/c-Si heterojunction MAGFETs with an L ： W ratio of 4 ： 1 are in series, their magnetic sensitivity is 22.74 mV/T, which is an improvement of about 64% compared with that of a single nc-Si/c-Si heterojunction MAGFET.

Performance prediction of four-contact vertical Hall-devices using a conformal mapping technique

Instead of the conventional design with five contacts in the sensor active area, innovative vertical Hall devices （VHDs） with four contacts and six contacts are asymmetrical in structural design but symmetrical in the current flow that can be well fit for the spinning current technique for offset elimination. In this article, a conformal mapping calculation method is used to predict the performance of asymmetrical VHD embedded in a deep n-well with four contacts. Furthermore, to make the calculation more accurate, the junction field effect is also involved into the conformal mapping method. The error between calculated and simulated results is less than 5% for the currentrelated sensitivity, and approximately 13% for the voltage-related sensitivity. This proves that such calculations can be used to predict the optimal structure of the vertical Hall-devices.