  Van der Waals magnets are uniquely positioned at the intersection between
two-dimensional materials, antiferromagnetic spintronics, and magnonics. The
interlayer exchange interaction in these materials enables antiferromagnetic
resonances to be accessed at GHz frequencies. Consequently, these layered
antiferromagnets are intriguing materials out of which quantum hybrid magnonic
devices can be fashioned. Here, we use both a modified macrospin model and
micromagnetic simulations to demonstrate a comprehensive antiferromagnetic
resonance spectra in van der Waals magnets near the ultrathin (monolayer)
limit. The number of optical and acoustic magnon modes, as well as the mode
frequencies, are found to be exquisitely sensitive to the number of layers. We
discover a self-hybridization effect where pairs of either optical or acoustic
magnons are found to interact and self-hybridize through the dynamic exchange
interaction. This leads to characteristic avoided energy level crossings in the
energy spectra. Through simulations, we show that by electrically controlling
the damping of surface layers within heterostructures both the strength and
number of avoided energy level crossings in the magnon spectra can be
controlled.
