Unveiling magnetic phases and chiral spin dynamics: re-order parameters and spin wave handedness

We introduce a dynamic nonequilibrium order parameter, termed the re-order parameter to capture subtle magnetic phase transitions in strongly spin-orbit-coupled magnets. By applying this approach to orthoferrites YFeO₃ and Mn-doped variants, we uncover previously hidden phases, such as a ferrimagnetic state within the collinear antiferromagnetic phase, through the analysis of low-energy magnon dynamics. These findings allow for the construction of detailed magnetic phase diagrams, highlighting the potential of the re-order parameter to reveal new phases in complex magnetic materials [1]. In parallel, we employ terahertz (THz) time-domain spectroscopy to directly observe the handedness reversal of coherent spin waves across compensation temperatures in ferrimagnets [2]. This real-time observation technique provides new insights into chiral spin dynamics, complementing the phase transition studies by offering a dynamic view of spin behavior. Together, these methods deepen the understanding of magnetic phenomena, from phase transitions to spin wave dynamics, offering novel tools for exploring the intricate behavior of interacting magnets.

References:

[1] B. C. Park, et al. Nature communications 15, 3294 (2024)

[2] T. Ha, et al. npj Spintronics 2, 37 (2024)