Research: 1/5 and 1/3 magnetization plateaux in the spin 1/2 chain system YbAlO3

YbAlO₃ is a quasi-one-dimensional spin-chain material that has an unusual phase diagram at very low temperature and in magnetic field. It orders antiferromagnetically below 0.9 K and, most interestingly, switches to a spin-density wave state in a small magnetic field.

This state was shown to be stabilised by anisotropic interchain interactions. In contrast to the few other materials in which this state exists, in YbAlO₃ a magnetisation plateau at 1/3 of the saturation value was observed, but its origin remained unclear. In this paper, we show experimental evidence from thermal conductivity, magnetostriction and ac-susceptibility of 1/3, 1/5 and 1/7 magnetisation plateaux in YbAlO₃. 
This is the first experimental observation of multiple plateaux states in a quasi -one-dimensional quantum magnet.

Furthermore, we show by phenomenological theory that the plateaux stability is a consequence of the fact that interchain interactions are ferromagnetic in this material.

P. Mokhtari, S. Galeski, U. Stockert, S. E. Nikitin, R. Wawrzynczak, R. Kuechler, M. Brando, L. Vasylechko, O. A. Starykh, E. Hassinger,
1/5 and 1/3 magnetization plateaux in the spin 1/2 chain system YbAlO₃,
Phys. Rev. Lett. 135, 076704 (2025) (arXiv)