Leonie Heinze

Forschungszentrum Jülich, JCNS at MLZ, Garching, Germany

Frustrated magnetism in quantum spin chain materials

In this talk, I will report on two minerals which have been established as quantum spin chain materials in the past. In atacamite Cu₂Cl(OH)₃, the largest exchange interactions by far couple the Cu spins into antiferromagnetic quantum sawtooth chains [1] leading to geometrical frustration in the material. Whilst long-range magnetic order is present below T_N = 8.9 K because of weak residual couplings, the order can be suppressed in magnetic fields of 21.9 T (H || c axis), far away from the field where full field polarization is expected for the material. Here, I will discuss how those elevated magnetic fields act as tuning parameter driving atacamite into this disorganized but still correlated spin state. In linarite, PbCuSO₄(OH)₂, frustration arises because of competing ferromagnetic and antiferromagnetic exchange interactions [2]. Directly below full field polarization, its complex magnetic phase diagram is predicted to contain a spin-multipolar phase. I will present here applied-field neutron diffraction and spectroscopy studies we have carried out in the past to find evidence for this unusual spin state [3,4].

[1] L. Heinze et al., Phys. Rev. Lett. 126, 207201 (2021).

[2] A. U. B. Wolter et al., Phys. Rev. B 85, 014407 (2012).

[3] L. Heinze et al., Phys. Rev. B 99, 094436 (2019).

[4] L. Heinze et al., Phys. Rev. B 106, 144409 (2022).