Complex Field-Induced States in Linarite PbCuSO4(OH)2 with a Variety of High-Order Exotic Spin-Density Wave States

Low-temperature neutron diffraction and NMR studies of field -induced phases in linarite are presented for magnetic fields Hub axis. A two-step spin -flop transition is observed, as well as a transition transforming a helical magnetic ground state into an unusual magnetic phase with sine -wave-modulated moments IIH. An effective (J) over tilde (1)-(J) over tilde (2) single-chain model with a magnetization -dependent frustration ratio alpha(eff) = -(J) over tilde (2)/(J) over tilde (1) is proposed. The latter is governed by skew interchain couplings and shifted to the vicinity of the ferromagnetic critical point. It explains qualitatively the observation of a rich variety of exotic longitudinal collinear spin -density wave, SDWp, states (9 >= L p >= 2).