Pentamers of transition metal octahedra and double semihelical chains of hydrogen bonds frame hureaulite-type oxyhydroxides (C2/c; a = 11.5 Å, b = 9.1 Å, c = 9.5 Å, beta = 96.4°) highly interesting for rich magnetic spin orders and polaron-dependent charge transport phenomena. Neutron powder diffraction data of its manganese end-member agree with that the magnetic lattice retains the (1a x 1b x1c) unit cell below the Curie temperature 7.2 K down up to 2 K, but magnetic moments of Mn2+ within MnO6 pentamers oriented predominantly parallel to the crystallographic b axis vividly change on to the (a-c) plane at lowered temperatures. The respective ferrimagnetic order corresponds to the magnetic space group C2/c at 6.5 K (Figure 1a) and C2’/c’ at 3.4 K (Figure 1b). This reflects complicated discontinuity curves of AC magnetic susceptibility. Another phase transition occurs around at 2 K, where the magnetic spins are incommensurately modulated with a propagation vector (0.545(2), 0, ~0).
We present here subtle details of a complex evolution of magnetic spin orders of the title compound along with briefing quasi- and inelastic neutron scattering studies to demonstrate mechanism for the ease with protonic superconductivity.