Radio frequency microwave detector is an important electronic device in microwave system. It has wide application in communication, radar, navigation, remote sensing, electronics industry, medical treatment and scientific research. In recent years, with the rapid development of communication technology, higher requirements for future microwave detectors are put forward, such as high sensitivity detection for weak signals (below μW), low power consumption and easy miniaturization and integration. The use of electron spin properties rather than electronic charge properties to build microwave detectors is expected to solve the above challenges.

Recently, Zeng Zhongming team of Suzhou Institute of Nanotechnology and Nanostructure Biology, Chinese Academy of Sciences, has made new progresses in the research on microwave detection devices based on electron spin characteristics in cooperation with domestic and foreign scientists. They use thin film preparation technology to precisely control the interface properties of nano-magnetic thin films. The magnetic moments of the free layer are subtly perpendicular to the film plane in the "magnetic free layer / isolation / magnetic fixed layer" sandwich nanostructures. The magnetic moment of the fixed layer Parallel to the film plane (Figure a). Since the magnetic moments of the two magnetic layers are arranged nearly 90 degrees, the spin injection efficiency is greatly improved. The structure offers excellent microwave detection performance: up to 75,400 mVmW-1 at 1 nW of weak signal, 20 times the detection limit of a semiconductor Schottky diode detector. At the same time, the device is the volume of semiconductor microwave detectors 1/50, easy to integrate. In addition, the device can work under zero magnetic field, eliminating the dependence on the external magnetic field, simplifying the device structure, reducing power consumption. The results of this study provide important guidance for the design of new and highly sensitive nano-devices. Relevant research results published in the recent Nature Communications (Nature Communications, 2016, 7: 11259).

The work of this research has been funded by the Ministry of Science and Technology major instruments and the National Natural Science Foundation.

(A) Schematic diagram of device structure and test principle; (b) Microwave response curve under different applied bias currents

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