Abstract: The increased demand for memory-intensive computing systems with low energy dissipation has accelerated research on memory technologies based on new materials that can complement or replace existing semiconductor solutions. Among magnetic materials, antiferromagnets (AFM) have emerged as a strong candidate with potential for neuromorphic computing, ultrafast memory devices, and high-frequency (terahertz) electronics. The main properties that make AFMs of high interest for these applications are their ultrafast dynamics at the picosecond time scale (high-speed devices), the possibility to construct high-density device arrays without coupling between adjacent devices (high-density architectures), immunity against external magnetic fields, and the possibility to detect and generate terahertz signals at the nanoscale (terahertz nano-oscillators and spin diodes). To integrate AFMs in computing architectures, AFM-based devices need physical mechanisms for both writing and reading that are energy-efficient and fast, allowing storage and manipulation of information through the Néel vector order parameter.

In this talk, I will focus on the first aspect, the electrical manipulation of metallic antiferromagnets which are compatible with complementary metal-oxide semiconductor (CMOS) manufacturing technology. First, I will talk about my recent results on the current-induced switching of PtMn micropillars 5 grown on Pt, where the switching mechanism is spin-orbit torque (SOT). The results demonstrate the effective manipulation of the metastable states of PtMn, associated with small changes of the domain structure, by low-amplitude electric current pulses, 2 MA cm-2. These are much lower than the typical current densities used for switching insulating AFMs such as NiO, 40 MA cm-2. Besides, the proposed device shows interesting dual characteristics with potential for neuromorphic applications: 1) At fixed current amplitudes the device acts as a binary memory (two well-defined states). 2) For current pulses where the amplitude is progressively modified, the resistance of the device changes as an analog memory (i.e., memristor), allowing the possibility to use this device as a synapse for neuromorphic computing.

Next, I will focus on the electrical manipulation of non-collinear AFMs, specifically in IrMn3 micropillars 6. In this case, I will discuss the anatomy of the current-induced switching of IrMn3 by extrinsic SOT generated by moderate current pulses, 20 MA cm-2 amplitude, in a pioneering double cross bar structure. In this new structure, it is possible to distinguish and eliminate parasitic signals associated with thermal effects and reversible electromigration processes, which can hide the AFM switching signatures. I will demonstrate that the current-induced switching, in this case, takes place by the displacement of domain walls assisted by the Joule heating generated by the current pulse.

Finally, I will talk about the possible new routes that AFM spintronics can take towards lower energy dissipative devices. As an illustrative case, I will discuss my numerical results on the voltage control of the magnetic anisotropy of metallic AFMs as a low-energy mechanism to re-orient the Néel vector in picosecond time scales (below 20 ps) with ~250 aJ per bit 7.