Magnetic Phase Diagram Of The Frustrated Spin Chain Compound Linarite Pbcuso4(Oh)(2) As Seen By Neutron Diffraction And H-1-Nmr

We report on a detailed neutron diffraction and H-1-NMR study on the frustrated spin-1/2 chain material linarite, PbCuSO4(OH)(2), where competing ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor interactions lead to frustration. From the magnetic Bragg peak intensity studied down to 60 mK, the magnetic moment per Cu atom is obtained within the whole magnetic phase diagram for H vertical bar vertical bar b axis. Further, we establish the detailed configurations of the shift of the SDW propagation vector in phase V with field and temperature. Finally, combining our neutron diffraction results with those from a low-temperature/high-field NMR study, we find an even more complex phase diagram close to the quasisaturation field suggesting that bound two-magnon excitations are the lowest energy excitations close to and in the quasisaturation regime. Qualitatively and semiquantitatively, we relate such behavior to XYZ exchange anisotropy and contributions from the Dzyaloshinsky-Moriya interaction to affect the magnetic properties of linarite.