Fig. 5. Magnetic state of barlowite 2 elucidated by magnetic neutron diffraction on a single crystal.

a Longitudinal scans through the [0.5 0.5 0] and [1 1 0] magnetic Bragg peaks measured at T = 2.7 and 8 K with E_i = 5 meV at SPINS, where the T = 20 K data was subtracted as background. The red lines are Gaussian fits. The horizontal bars indicate the experimental resolution, and the error bars represent one standard deviation. b Temperature dependences of the peak intensities of the [0.5 0.5 0] and [1 1 0] magnetic Bragg peaks measured at E = 5 meV (SPINS) and E_i = 14.7 meV (BT-7). The top panel also displays the squared magnetization (M²) of a single crystal in the ab plane at μ₀H = 0.005 T. Below T = 6 K, the red line in the bottom panel is a power-law fit from T = 2–11 K with critical exponent β = 0.30(3) and T_N = 6; above T = 6 K the line is a guide to the eye. c The pinwheel q = 0 magnetic model of barlowite 2 in the ab plane and along c (inset). d The magnetic model proposed for orthorhombic barlowite 1 by ref. ³⁵ overlaid on our barlowite 1 crystal structure. All occupancy values are taken from SCXRD (Supplementary Table 3). For c and d, the arrows indicate the sizes and directions of the moments. Dark and light blue spins represent interlayer Cu²⁺s in different layers, while red and green spins represent kagome Cu²⁺s. Each interlayer motif is visualized by one spin at the weighted center of the sites. The thickness of the lines between kagome spins indicates relative bond strength extracted from the Cu–O–Cu bond angles. The ± symbols next to the kagome spins denote the directions of the out-of-plane component in the spins. The dashed lines denote the magnetic unit cell.