The pulsed high magnetic field facility and scientific research at Wuhan National High Magnetic Field Center

Wuhan National High Magnetic Field Center(WHMFC)at Huazhong University of Science and Technology is one of the top-class research centers in the world,which can offer pulsed fields up to 90.6 T with different field waveforms for scientific research and has passed the final evaluation of the Chinese government in 2014.This paper will give a brief introduction of the facility and the development status of pulsed magnetic fields research at WHMFC.In addition,it will describe the application development of pulsed magnetic fields in both scientific and industrial research.

The Magnetic Anisotropy and Complete Phase Diagram of CuFeO2 Measured in a Pulsed High Magnetic Field up to 75 T

The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin- flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.

Unconventional room-temperature negative magnetoresistance effect in Au/n-Ge:Sb/Au devices

Non-magnetic semiconductor materials and their devices have attracted wide attention since they are usually prone to exhibit large positive magnetoresistance(MR)effect in a low static magnetic field environment at room temperature.However,how to obtain a large room-temperature negative MR effect in them remains to be studied.In this paper,by designing an Au/n-Ge:Sb/Au device with metal electrodes located on identical side,we observe an obvious room-temperature negative MR effect in a specific 50 T pulsed high magnetic field direction environment,but not in a static low magnetic field environment.Through the analysis of the experimental measurement of the Hall effect results and bipolar transport theory,we propose that this unconventional negative MR effect is mainly related to the charge accumulation on the surface of the device under the modulation of the stronger Lorentz force provided by the pulsed high magnetic field.This theoretical analytical model is further confirmed by regulating the geometry size of the device.Our work sheds light on the development of novel magnetic sensing,magnetic logic and other devices based on non-magnetic semiconductors operating in pulsed high magnetic field environment.

Magnetoresistance retraction behaviour of Ag/p-Ge:Ga/Ag device under pulsed high magnetic field

In non-magnetic semiconductor materials,unsaturated magnetoresistance(MR)effect has attracted lots of attention due to its physical interests and potential applications in electronic devices.Under the ex-tremely high magnetic field,the stability and reliability of MR effects based on the non-ohmic transport has been rarely researched.In this paper,the transport properties of non-magnetic Ag/p-Ge:Ga/Ag devices under 45 T pulsed high magnetic field at 300 K are investigated.It is found that in ohmic conduction re-gion(I<5 mA)where the single dominant carrier is hole,the MR values increase with increasing the applied magnetic field,presenting a conventional unsaturated behavior.In the two non-ohmic regions(5 mA≤I≤100 mA)where the transport is dominated by bipolar(electrons and holes),a MR retraction has been obviously observed under pulsed high magnetic field.Combining the Hall measurement results and calculation of Hall effect with bipolar-driven transport model,the mechanism of the MR retraction is analysed,in which the MR retraction may be related to the strong regulation of electron-to-hole den-sity ratio by pulsed high magnetic field.This work provides a reference for evaluating the stability and reliability of the properties of non-magnetic semiconductor based MR devices under the interference of strong magnetic pulses.