Magnetic phase diagram of the strongly frustrated quantum spin chain system PbCuSO${}_4$(OH)${}_2$ in tilted magnetic fields

We report the $\mathbf{H}-T$ phase diagram of $S=1\mathrm{/}2$ strongly frustrated anisotropic spin chain material linarite PbCuSO${}_4$(OH)${}_2$ in tilted magnetic fields up to 10 T and temperatures down to 0.2 K. By means of torque magnetometry we investigate the phase diagram evolution as the magnetic field undergoes rotation in ${\mathbf{b}\mathbf{a}}^{\ast }$ and $\mathbf{b}\mathbf{c}$ planes. The key finding is the robustness of the high field spin density wave-like phase, which may persist even as the external field goes orthogonal to the chain direction $\mathbf{b}$. In contrast, the intermediate collinear antiferromagnetic phase collapses at moderate deflection angles with respect to $\mathbf{b}$ axis.