Magnetic structure and high-field magnetization of the distorted kagome lattice antiferromagnet Cs2Cu3SnF12

High-resolution time-of-flight powder neutron diffraction and high-field magnetization were measured to investigate the magnetic structure and existence of a field-induced magnetic phase transition in the distorted kagome antiferromagnet ${\mathrm{Cs}}₂{\mathrm{Cu}}₃{\mathrm{SnF}}₁₂$. Upon cooling from room temperature, the compound undergoes a structural phase transition at ${T}_{\mathrm{t}}=185\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ from the rhombohedral space-group $R\overline{3}m$ with the perfect kagome spin network to the monoclinic space-group $P{2}₁/n$ with the distorted kagome planes. The distortion results in three inequivalent exchange interactions among the $S=1/2\phantom{\rule{0.28em}{0ex}}{\mathrm{Cu}}²⁺$ spins that magnetically order below ${T}_{\mathrm{N}}=20.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. Magnetization measured with a magnetic field applied within the kagome plane reveals small in-plane ferromagnetism resulting from spin canting. On the other hand, the out-of-plane magnetization does not show a clear hysteresis loop of the ferromagnetic component nor a prominent anomaly up to 170 T with the exception of the subtle kneelike bend around 90 T, which could indicate the 1/3 magnetization plateau. The combined analysis using the irreducible representations of the magnetic space groups and magnetic structure refinement on the neutron powder-diffraction data suggests that the magnetic moments order in the magnetic space-group $P{2}₁^{\ensuremath{'}}/{n}^{\ensuremath{'}}$ with the all-in--all-out spin structure, which by symmetry allows for the in-plane canting, consistent with the in-plane ferromagnetism observed in the magnetization.