Abstract
Microwave detectors based on the spin-torque diode effect are among the key emerging spintronic devices. By utilizing the spin of electrons in addition to charge, they have the potential to overcome the theoretical performance limits of their semiconductor (Schottky) counterparts. However, so far, practical implementations of spin-diode microwave detectors have been limited by the necessity to apply a magnetic field. Here, we demonstrate nanoscale magnetic tunnel junction microwave detectors, exhibiting high-detection sensitivity of 75,400 mV mW−1 at room temperature without any external bias fields, and for low-input power (micro-Watts or lower). This sensitivity is significantly larger than both state-of-the-art Schottky diode detectors and existing spintronic diodes. Micromagnetic simulations and measurements reveal the essential role of injection locking to achieve this sensitivity performance. This mechanism may provide a pathway to enable further performance improvement of spin-torque diode microwave detectors.
Highlights
Microwave detectors based on the spin-torque diode effect are among the key emerging spintronic devices
The spin-torque diode effect is the result of spintorque-induced ferromagnetic resonance (FMR), which leads to a rectification effect in magneto-resistive nanoscale devices
The devices studied in this work have an magnetic tunnel junctions (MTJs) structure consisting of a synthetic antiferromagnetic Co70Fe30 (2.3 nm)/Ru (0.85 nm)/Co40Fe40B20 (2.4 nm) reference layer, exchange biased by a PtMn film, designed to have an in-plane easy axis, and a Co20Fe60B20 perpendicularly magnetized free layer, separated from the reference layer by a 0.8 nm MgO tunnel barrier
Summary
Microwave detectors based on the spin-torque diode effect are among the key emerging spintronic devices. We demonstrate nanoscale magnetic tunnel junction microwave detectors, exhibiting high-detection sensitivity of 75,400 mV mW À 1 at room temperature without any external bias fields, and for low-input power (micro-Watts or lower). This sensitivity is significantly larger than both state-of-theart Schottky diode detectors and existing spintronic diodes. In spin-torque diodes studied so far, the application of an additional external magnetic field (often canted at an angle with respect to the device plane) is required to achieve large microwave detection sensitivity[21,23,24,25,26,27,28]. The operation mechanism and the fundamental role of the injection locking are discussed on the basis of measurements combined with micromagnetic simulations
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