Fig. 1

Field-evolution of the zigzag order in α-RuCl₃: Bulk susceptibility and diffraction are shown as a function of magnetic field b applied along a reciprocal {110} direction. Note that the {110} is equivalently one of (1, 1, 0), (−1, 2, 0) or (2, −1, 0) directions. a Néel temperature vs. b determined from the local maximum in temperature-dependent magnetic susceptibility curves measured in fixed fields (i.e., where dχ/dB = 0) Error bars are determined from the FWHM of a Gaussian fit to the peak in the derivative d²χ/dB² at the local maximum point (inset). For each field, χ (T) was collected on warming after cooling in zero magnetic field. The region below the experimental base temperature is indicated by hash marks. b Schematic of the magnetic field direction in the honeycomb plane. c Magnetic Bragg peak intensity normalized to the zero-field value (i.e., I(B)/I(B = 0)). The field is applied in the (−1, 2, 0) direction perpendicular to the (H, 0, L) plane. Blue diamonds show the suppression of the in-plane (1/2, 0, 1) magnetic peaks in two different crystals, ‘Xtal1’ and ‘Xtal2’, measured at HYSPEC (solid symbols) and CORELLI (open symbols). The green circles show the out-of-plane magnetic peak at (−1/2, 1/2, 1) measured at CORELLI (See Methods for instrument parameters). The yellow symbols represent the weighted average intensity over magnetic peaks with L = 1. In this average, the peaks within the (H, 0, L) plane contribute 1/3 of the intensity. Solid lines are a guide to the eye. Error bars represent one standard deviation assuming Poisson counting statistics