Superconducting quantum interference device (SQUID) has extremely high magnetic field sensitivity, current sensitivity, and can detect a low-noise weak current signal. The SQUID current sensor has become the only option of the readout of low-noise detector, such as transition-edge sensor (TES). In this paper, a second-order gradiometric cross-coupled SQUID current sensor for TES application is developed. According to the requirements for TES detectors, the structure and various parameters of SQUID current sensor are designed. The SQUID loop, input coil and feedback coil of the SQUID current sensor all use the second-order gradiometric structure. All the couple ways between SQUID loop and input coil or feedback coil adopt cross-coupling mode in different planes, which can effectively weaken the parasitic capacitance. A second-order gradiometric cross-coupled SQUID current sensor based on Nb/Al-AlO<i><sub>x</sub></i>/Nb Josephson junction is successfully fabricated on a silicon wafer by optimizing the process. The properties of the second-order gradiometric cross-coupled SQUID current sensor are measured at liquid helium temperature. The bias current of SQUID is 215 μA when the modulation depth of <i>V</i>-<i>Φ</i> modulation curve is maximum. The maximum modulation peak of SQUID is 31 μV. The flux-to-voltage transfer coefficient of SQUID is 108 μV/<i>Φ</i><sub>0</sub>. The input coil current sensitivity is 17 μA/<i>Φ</i><sub>0</sub>, the mutual inductance between SQUID loop and input coil is 117 pH. The current sensitivity of feedback coil is 86 μA/<i>Φ</i><sub>0</sub>, the mutual inductance between SQUID loop and feedback coil is 23 pH. The second-order gradiometric cross-coupled SQUID current sensor has a white flux noise of 2 μ<i>Φ</i><sub>0</sub>/<inline-formula><tex-math id="M3">\begin{document}$ \sqrt{{\rm{H}}{\rm{z}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M3.png"/></alternatives></inline-formula> and a white current noise of 34 pA/<inline-formula><tex-math id="M4">\begin{document}$ \sqrt{{\rm{H}}{\rm{z}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20201816_M4.png"/></alternatives></inline-formula> with 1/<i>f</i> corner frequency around 200 Hz. The result of noise level under the condition without magnetic shielding shows that the SQUID current sensor with second-order gradiometric cross-coupled structure has an excellent capability of weakening the environmental electromagnetic interference. In the future, we will further improve the mutual inductance of the second-order gradiometric cross-coupled SQUID current sensor between SQUID loop and input coil, optimize the size and critical current of Josephson junction, in order to improve the input sensitivity of SQUID device, reduce the current noise level and the 1/<i>f</i> corner frequency, and meet more requirements for TES applications.
Because of the strong coupling between the magnetic and dielectric properties, the study of quantum paraelectric EuTiO3 has attracted more and more attention in both theoretical and experimental research recently. In this paper, the first principles based on the density functional theory within the generalized gradient approxiamtion is used to investigate the magnetic and electronic structure of quantum paraelectric EuTiO3, and to analyze the effects of the strain on the magnetic and strutural phase transition, in turn to discuss the possible magnetoelectric coupling mechanism of this material. The calculations show that EuTiO3 with the strain-free is in a paraelectric cubic and G-type antiferromagnetic state at low temperature, while appling either compressive or tensile strain along the c-axis to it, the balance of hybridization between Ti 3d and O 2p orbit will be breaken and EuTiO3 will transite from paraelectric and G-antiferromagnetic to ferroelectric-ferromagnetic structure as the strain is increased to a certain value. All those indicate the strong spin-lattice coupling effect in EuTiO3.
New retail is a retail model based on the Internet, using big data, cloud computing and other technologies to upgrade the production process, circulation and sales of commodities, and deep integration of online and offline and smart logistics. The new retail has aroused widespread concern from all walks of life, and the new retail industry has sprung up, which has also promoted the development of new logistics. By analyzing the relationship between new retail and new logistics development, the article explores the relationship and difference between new logistics and traditional logistics, analyzes the motivation of new logistics development, and proposes relevant measures to promote the development of new logistics.
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