Phase Diagram of $\alpha$-RuCl$_3$ in an in-plane Magnetic Field

Understand

The low-temperature magnetic phases in the layered honeycomb lattice material $\alpha$-RuCl$_3$ have been studied as a function of in-plane magnetic field.

• In zero field this material orders magnetically below 7 K with so-called zigzag order within the honeycomb planes.
• Neutron diffraction data show that a relatively small applied field of 2 T is sufficient to suppress the population of the magnetic domain in which the zigzag chains run along the field direction.
• We found that the intensity of the magnetic peaks due to zigzag order is continuously suppressed with increasing field until their disappearance at $\mu_o$H$_c$=8 T.