Magnetic-field tuning of the spin dynamics in the quasi-2D van der Waals antiferromagnet CuCrP$_{2}$S$_{6}$
The use of antiferromagnets in magnetoelectronic devices as counterparts of ferromagnets is a new, rapidly developing trend in spintronics that leverages antiferromagnetic (AFM) magnons for transmitting of spin currents. Van der Waals (vdW) antiferromagnets are particularly attractive in this respect as they possess tunable magnetic properties and can be easily integrated into spintronic devices. In this work we use electron spin resonance (ESR) spectroscopy to assess the potential of the vdW AFM compound CuCrP$_{2}$S$_{6}$ for magnonic applications by exploring the magnetic field ($H$) dependence of the spectrum of magnon excitations below its AFM ordering temperature $T_{\rm N} \approx 30$ K and the correlated spin dynamics above $T_{\rm N}$. ESR reveals prominent ferromagnetic (FM) spin correlations that persist far above $T_{\rm N}$ suggesting an intrinsically two-dimensional character of the spin dynamics in CuCrP$_{2}$S$_{6}$. Most interestingly, at $T < T_{\rm N}$, CuCrP$_{2}$S$_{6}$ features two non-degenerate, i.e., distinct in energy AFM magnon modes at $H = 0$ which can be tuned to the FM type of collective spin excitations with increasing $H$. These remarkable properties are favorable for the induction and control of unidirectional spin current in CuCrP$_{2}$S$_{6}$ and suggest it as a new functional material for magnetoelectronics.