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VIDEO DOI: https://doi.org/10.48448/53z2-ss16

technical paper

MMM 2022

November 07, 2022

Minneapolis, United States

Injection Locking of Antiferromagnetic Oscillators

Spin Hall antiferromagnetic oscillators (AFMO) (1) are a promising candidate for a CMOS-compatible THz-range frequency source. The output power of a nano-scale AFMO is relatively low, and mutual synchronization of AFMOs may be used to increase the power and to reduce the generation linewidth. The first step in understanding AFMO synchronization is to investigate the injection locking of a single oscillator, i.e., synchronization to an external driving signal. Here, we numerically study the injection locking of AFMOs using the model derived in (1). In contrast with previous studies (2, 3), we study injection locking in a wide range of AFMO frequencies and assume that the driving signal is mixed with the DC bias current, i.e., that the bias and locking spin currents have the same spin polarization, which is more suitable for practical realization. Figure 1 shows a dependence of the driven AFMO frequency f on the injected frequency fs. Straight segment near the AFMO free-running frequency f0 = 0.23 THz corresponds to the injection locking at the fundamental signal harmonic. The huge locking bandwidth Δf1≈100 GHz is due to strong influence of AFMO nonlinearity related to anisotropy of the antiferromagnet (1). An additional signature of a strongly nonlinear regime is the appearance of higher-order locking bands f=2fs and f=3fs. Synchronization at higher harmonics may be important in practical applications, since it allows one to synchronize THz-range AFMO by a driving signal of a lower frequency. The synchronization bandwidth Δf1 drastically reduces with the increase of AFMO free-running frequency f0 (Fig. 2). This effect is caused by reduction of AFMO nonlinearity and may be a serious obstacle for practical use of AFMOs in the frequency range f > 1 THz. Therefore, alternative methods of AFMO injection locking should be studied, such as locking to a microwave magnetic field or to a spin current with different spin polarization (2).

(1) R. Khymyn, et al., “Antiferromagnetic THz-frequency Josephson-like oscillator driven by spin current”, Sci. Rep. 7, 43705 (2017).
(2) O. Gomonay, T. Jungwirth, and J. Sinova, “Narrow-band tunable terahertz detector in antiferromagnets via staggered-field and antidamping torques”, Phys. Rev. B 98, 104430 (2018).
(3) R. Khymyn, et al., “Injection-locking of a nonlinear sub-THz antiferromagnetic spin-Hall oscillator”, DE-08, Abstracts of the International Magnetics Conference INTERMAG-18, Singapore, Singapore, April 2018.


Transcript English (automatic)

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