Nanoscale physics

Antiferromagnetic tunnel junction as a key-element of nanoscale THz-frequency signal source
O. Sulymenko1, O. Prokopenko1
1Faculty of Radio Physics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska Street, Kiev-01601, Ukraine
E-mail: olgasulymenko@gmail.com

We propose a novel type of a terahertz-frequency signal source based on an antiferromagnetic tunnel junction (ATJ), where the generated ac signal is extracted through the variations of the tunneling anisotropic magnetoresistance (TAMR) of an ATJ. The signal source consists of a current-driven platinum (Pt) layer and a layer of an antiferromagnet (AFM) separated by a MgO spacer from an additional Pt electrode. A dc electric current flowing in the first Pt layer creates a perpendicular spin current due to the spin Hall effect [1], that, being injected in the AFM layer, tilts the magnetizations of the AFM sublattices, and, therefore, causes THz-frequency precession of these magnetizations. This precession, through the TAMR effect [2], causes the THz-frequency variations of the total resistance of the layered structure. Our calculations show that such a source could provide an output power exceeding 1 µW at the frequency of 0.5 THz (for a junction having optimal thickness of MgO barrier and junction’s cross-section area) and could be promising for experimental realization at micro- and nano-scale.
Although the efficiency of the proposed TAMR method of the THz-frequency ac signal extraction from an ATJ is reduced with the increase of the generation frequency, we believe, that this method could be used for the generation of signals with frequencies of up to 10 THz due to its relative simplicity and convenience.
We would like to acknowledge Prof. A.N. Slavin and Dr. V.S. Tyberkevych (Oakland University, Rochester, MI, USA) for fruitful discussions. The publication contains the results of studies conducted by President’s of Ukraine grant for competitive projects (F 78) and is also based on the research provided by the grants F 76/34-2018 and F 83 of the State Fund for Fundamental Research of Ukraine. This work was also supported in part by the grants 16BF052-01 and 18BF052-01M from Taras Shevchenko National University of Kyiv and grant 7F from the National Academy of Sciences of Ukraine.
1.	Sinova J. et al. Spin Hall effects // Rev. Mod. Phys.-2015.-87.-P. 1213-1259.
2.	Wadley P. et al. Electrical switching of an antiferromagnet // Science.-2016.-351.-P. 587–590.