Nanoscale physics

Detection of Monochromatic and Pulsed Input Signals in Spin-Torque Diode
Artemchuk P.Yu.1, Prokopenko O.V.1
1 Faculty of Radio Physics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv. Volodymyrska str., 64/13, Kyiv-01601, Ukraine.
E-mail: doompeter@ukr.net
A magnetic tunnel junction generate output dc voltage in response on the input microwave signal and can be used as a detector of microwave signals. This device usually called a spin-torque diode (STD). STD operation based on the spin-torque diode effect [1] utilizing the spin-transfer-torque effect an the tunneling magnetoresistance effect. Having volt-watt sensitivity that exceeds that of the state-of-the art Shottky diodes[2], STD is a promising candidate to replace them in the future.
Typically one considers STD operation under input microwave signal of a constant amplitude over a relatively long period of time. Many of communication and radar systems use microwave frequency range. Thus, they might be candidates for STD application. At the same time, most of the signals used on practice are pulsed or modulated. Due to the difference between monochromatic microwave signal and microwave pulses of different profile or modulated signal the STD may provide unpredictable output dc voltage response or distorted pulse profile .
In this work the output dc voltage response of the STD to the input microwave signal pulse of different power, frequency, length and profile has been investigated. Rectangle pulse has been shown to make good response but the fronts might be distorted depending on the input power level.  Response to pulse of other shape (for example - triangle) more dependent on the input pulse power and frequency and distorions might be significant.

1.	Tulapurkar A.A., Suzuki Y., Fukushima A., Kubota H., Maehara H., Tsunekawa K., Djayaprawira D.D., Watanabe N. & Yuasa S. Spin-torque diode effect in magnetic tunnel junctions // Nature.-2005.-438.-P. 339-342.
2.	Prokopenko O.V., Krivorotov I.N., Meitzler T.J., Bankowski E., Tiberkevich V.S., Slavin A.N. Spin-Torque Microwave Detectors // In book: Magnonics: From Fundamentals to Applications. Topics in Applied Physics (Vol. 125) / Eds. S.O. Demokritov and A.N. Slavin. -Berlin: Springer-Verlag, 2013. -P. 143-161.