Magnetic studies of monoclinic Cu₄O(SeO₃)₃, a copper-oxo-selenite derivative

¹ CFisUC, Department of Physics, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal
² C²TN, DECN, Instituto Superior Técnico, University of Lisbon, Estrada Nacional 10, 2695-066 Bobadela LRS, Portugal

^* Corresponding author: josemalta@ctn.tecnico.ulisboa.pt

Published online: 16 April 2020

Abstract

Cu₄O(SeO₃)₃ is a copper-oxo-selenite belonging to the Cu_xO(SeO₃)_(x–1) family of the topological chiral magnet Cu₂OSeO₃. We report magnetometry and specific heat data measured in a monoclinic Cu₄O(SeO₃)₃ single crystal grown through a Chemical Vapour Transport (CVT) reaction. Our study shows a typical antiferromagnetic behaviour, with a Néel temperature T_N = 58 K, similar to that of the Cu₂OSeO₃ and an additional transition at 13 K. The effective magnetic moment per Cu atom is 1.84 μ_B, close to the expected theoretical value for Cu²⁺. The low-temperature M(H) curves, show a transition starting at H_c1 ~ 400 Oe at 1.8 K shifting to a lower value of ~ 280 Oe at 30 K, likely from a helical into a conical intermediate phase, and a second transition at H_c2 ~ 1 kOe, above which the net moment increases linearly with applied field. The magnetisation moment value in a 90 kOe field is 0.053 μ_B/Cu at 1.8 K and attains a maximum value of 0.061 μ_B at 13 K. Low-temperature specific heat measurements confirm the presence of the magnetic transition at 13 K, slightly shifting to lower temperatures under an applied magnetic field.