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TT: Fachverband Tiefe Temperaturen

TT 9: Correlated Magnetism – Low-Dimensional Systems

TT 9.1: Vortrag

Montag, 17. März 2025, 15:00–15:15, H33

Pressure and quantum magnetism: Insights from brochantite Cu₄SO₄(OH)₆ — •Victoria Ginga¹, Bin Shen², Ece Uykur³, Nico Giordano⁴, and Alexander Tsirlin¹ — ¹Felix Bloch Institute, University of Leipzig, Germany — ²EP VI, EKM, University of Augsburg, Germany — ³Helmholtz-Zentrum Dresden-Rossendorf, Germany — ⁴Deutsches Elektronen-Synchrotron DESY, Germany

Brochantite Cu₄SO₄(OH)₆, a widespread natural copper sulfate mineral, exemplifies a low-dimensional quantum magnet due to its geometrically frustrated S = 1/2 Cu²⁺ chains. The crystal structure of brochantite (P2₁/n) consists of edge-sharing zigzag double chains forming corrugated sheets in the ab-plane, with dissimilar Cu-O-Cu bridges fostering complex magnetic interactions. Ferromagnetic ordering within the Cu1-Cu2 and Cu3-Cu4 chains coexists with antiferromagnetic coupling between the chains, thus creating a delicate balance that can be affected by external pressure. We show that brochantite develops antiferromagnetic ordering below T_N ≈ 6 K at ambient pressure. High-pressure X-ray diffraction data show that the monoclinic structure of brochantite remains stable up to at least 33 GPa, but individual structural parameters and especially bond angles are modified by pressure, thus affecting magnetic frustration in the compound. Magnetization measurements under pressure reveal changes in the Neel temperature and in the position of the susceptibility maximum. Our findings highlight brochantite as a platform for studying the interplay of structural and magnetic properties under extreme conditions.

Keywords: quantum magnetism; copper (II) mineral; low-dimensional magnet; magnetic frustration; magnetism under pressure