Terahertz-Frequency Signal Source Based on an Antiferromagnetic Tunnel Junction

We propose a novel type of terahertz-frequency (TF) 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 comprises a layered structure consisting of a current-driven platinum (Pt) layer and a layer of an antiferromagnet (AFM) separated by an MgO spacer from an additional Pt electrode. A dc electric current flowing in the first Pt layer due to the spin Hall effect creates a perpendicular spin current that, being injected in the AFM layer, tilts the magnetizations of the AFM sublattices and, therefore, causes TF rotation of these magnetizations in a large internal exchange magnetic field of the AFM. This rotation, through the TAMR effect, causes the TF variation of the total resistance of the layered structure. We evaluate the output power and efficiency of the above-described Pt/AFM/MgO/Pt TF signal source, and demonstrate that optimization of the source's geometrical parameters allows one to obtain the output power exceeding 1 μW at the frequency of 0.5 THz with the efficiency not smaller than 1%. Although the efficiency of the TAMR method of the TF signal extraction 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.