Low-lying magnetic excitations in the distorted triangular lattice antiferromagnet $\alpha$-CaCr$_2$O$_4$

We will discuss our results on $\alpha$-CaCr$_2$O$_4$ obtained by FIR and Terahertz spectroscopy. This compound orders below $T_{\mathrm{N}}$ = 42.6 K in a proper screw 120$^\circ$ magnetic order, but shows additional low-lying magnetic modes indicative for the vicinity of a more complex magnetic order [1-2]. Our spectra obtained by FTIR and THz-TD spectroscopy show several optical magnons appearing below the magnetic ordering with anomalous temperature dependence. We will discuss their polarization dependence and a possible magnetoelastic coupling of these modes.\\[4pt] [1] S. Toth et al., Phys. Rev. B 84, 054452 (2011)\\[0pt] [2] S. Toth et al., PRL 109, 127203 (2012)