Nonlinear amplification of microwave signals in spin-torque oscillators

• Published in: Nature communications Vol. 14; no. 1; pp. 2183 - 9
• Main Authors: Zhu, Keqiang, Carpentieri, Mario, Zhang, Like, Fang, Bin, Cai, Jialin, Verba, Roman, Giordano, Anna, Puliafito, Vito, Zhang, Baoshun, Finocchio, Giovanni, Zeng, Zhongming
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17.04.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 142/126; 639/166/987; 639/925/927/1062; Amplification; Amplifiers; CMOS; Design; Emissions; Frequency locking; Humanities and Social Sciences; Hybrid systems; multidisciplinary; Oscillators; Power consumption; Power management; Receivers & amplifiers; Science; Science (multidisciplinary); Spintronics; Stacks; Torque; Tunnel junctions; Wireless communications
• DOI: 10.1038/s41467-023-37916-9
• ISSN: 2041-1723

Spintronics-based microwave devices, such as oscillators and detectors, have been the subject of intensive investigation in recent years owing to the potential reductions in size and power consumption. However, only a few concepts for spintronic amplifiers have been proposed, typically requiring complex device configurations or material stacks. Here, we demonstrate a spintronic amplifier based on two-terminal magnetic tunnel junctions (MTJs) produced with CMOS-compatible material stacks that have already been used for spin-transfer torque memories. We achieve a record gain (| S 11  | > 2) for input power on the order of nW (<−40 dBm) at an appropriate choice of the bias field direction and amplitude. Based on micromagnetic simulations and experiments, we describe the fundamental aspects driving the amplification and show the key role of the co-existence in microwave emissions of a dynamic state of the MTJ excited by a dc current and the injection locking mode driven by the microwave input signal. Our work provides a way to develop a class of compact amplifiers that can impact the design of the next generation of spintronics-CMOS hybrid systems. Microwave devices are instrumental in wireless communications. Recently, spintronic-based microwave devices have seen significant interest, with the potential for smaller size, and lower power consumption. Here, Zhu et al demonstrate a spintronic amplifier with record gain, which uses material stacks already employed in industrially fabricated magnetic memories.