RF microwave detectors are important electronic devices in microwave systems and are widely used in communications, radar, navigation, remote sensing, electronics, medical, scientific research and other fields. In recent years, with the rapid development of communication technologies, higher demands have been placed on future microwave detectors, such as high sensitivity detection for weak signals (below μW), low power consumption, and ease of miniaturization and integration. The use of electron spin characteristics rather than electronic charge properties to construct microwave detectors is expected to solve the above challenges.
Recently, the Zeng Zhongming team of the Suzhou Institute of Nanotechnology and Nano-Bionics of the Chinese Academy of Sciences has cooperated with scientists at home and abroad to make new progress in the research of microwave detectors based on electron spin characteristics. They use the thin film preparation technology to precisely control the interfacial properties of the nanomagnetic film, and skillfully in the "magnetic free layer / isolation layer / magnetic fixed layer" sandwich nanostructure, the magnetic moment of the free layer is perpendicular to the film plane, and the magnetic moment of the fixed layer Parallel to the film plane (Fig. a). Since the magnetic moments of the two magnetic layers are arranged at nearly 90 degrees, the spin injection efficiency is greatly improved. The structure has excellent microwave detection performance: its detection sensitivity is as high as 75,400 mVmW-1 with a weak signal of 1 nW, which is 20 times the detection limit of the semiconductor Schottky diode detector. At the same time, the device is 1/50th the size of a semiconductor microwave detector and is easy to integrate. In addition, the device operates in a zero magnetic field, eliminating the dependence on external magnetic fields, simplifying device structure and reducing power consumption. The results of this study provide important guidance for designing new and highly sensitive nano-microwave devices. Related research results were published in recent recent Nature Communications (Nature Communications, 2016, 7: 11259).
The research work was funded by the Ministry of Science and Technology Major Instrument Special 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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