Microwave detectors based on the spin-torque diode effect

Abstract

The spin-transfer torque (STT) effect provides a new method of manipulation of magnetization in nanoscale objects. The STT effect manifests itself as a transfer of spin angular momentum between the parallel magnetic layers separated by a nonmagnetic spacer and traversed by a dc electric current. The transfer of the spin angular momentum from one layer to another could result in the excitation of the microwave-frequency magnetization dynamics in one of the magnetic layers. On the other hand, when a magnetization dynamics is excited in a magnetic layered structure by an external microwave signal both the structure electrical resistance and current through the structure will acquire microwave components resulting in the appearance of a rectified dc voltage on the magnetic structure. This "spin-torque diode effect" can be used for the development of ultra-sensitive spintorque microwave detectors (STMD). Below we present a brief review of our recent work on the general properties of STMDs, analyze the performance of the "resonance-type" and "threshold-type STMD" and consider the possible applications for such microwave detectors.

Spin‐Torque Diodes: From Fundamental Research to Applications

“…The one way to address this issue is to work in a broadband rectification regime, which can appear under specific conditions. [ 42 ] Although in case of this regime almost constant efficiency of rectification was demonstrated along the wide frequency range, the sensitivity revealed to be significantly lower than in resonant mode. In addition, to initiate broadband mode, one needs to apply rather high input RF power (about tens of microwatts) and therefore this mode is less attractive for ultralow power applications with power decreased down to nanowatts.…”

Synchronization of an Antiferromagnetic Josephson-like Oscillator with an External AC Signal

“…They are biased by a DC current and produce an output AC signal; hence, they can be used as nanoscale AC signal sources [6,7]. However, the same spintronic nanostructures can be used as passive (no DC current is applied) or DC biased AC signal detectors [8][9][10] and energy harvesters [8], which are able to convert an input AC signal to an output DC voltage, as well as other signal processing devices.…”

“…Nowadays spintronic oscillators, detectors and other devices mainly utilize ferromagnets [1][2][3][4][5][6][7][8][9][10][11]. Such systems are well studied experimentally [1-5, 8, 11] and theoretically or numerically [3,6,7,9,10]. However, these spintronic devices have at least one critical drawback: they can usually operate at frequencies less than ~ 50 GHz.…”

Recent Trends in Microwave Magnetism and Superconductivity

“…In contrast, in the OOP-regime, STMD operates as a threshold detector of low-frequency microwave signals, which might also be interesting for the energy harvesting applications [198]. The theory of STMD operation in both regimes is summarized in [201,202]. Also a promising novel type of frequencytunable STMD based on a rapidly-tuned STO has been recently proposed in [203].…”