Pb[Cu(SO4)(OH)2]: A Quasi One Dimensional S = 1/2 Magnet with Ferromagnetic Nearest Neighbor and Antiferromagnetic Next Nearest Neighbor Exchange Interactions

R. Szymczak, H. Szymczak Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland

G. Kamieniarz, G. Szukowski, K. Jaśniewicz Pacer, W. Florek Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland

V. Maltsev Department of Geology, Moscow State University, 119899 Moscow, Russia

and G.-J. Babonas Semiconductor Physics Institute, 2600 Vilnius, Lithuania

Received: October 28, 2008; In final form: March 25, 2009

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Magnetic properties of Pb[Cu(SO4)(OH)2] (linarite) natural single crystals were studied by magnetization and specific heat measurements. The angular dependences of magnetization were revealed which correlated with the regularities of the crystal structure. At about 2.8 K this quasi one dimensional Heisenberg system undergoes a phase transition to the long range antiferromagnetic order with antiparallel magnetic moments aligned probably along the b-axis. The antiferromagnetic order is evidenced by the metamagnetic transition and pronounced λ-type anomaly at TN in the specific heat. Using phenomenological modeling based on a quantum transfer matrix method, we argue that at higher temperatures linarite is a quasi one dimensional system with competing ferromagnetic nearest neighbor and antiferromagnetic next nearest neighbor exchange interactions.

DOI: 10.12693/APhysPolA.115.925 PACS numbers: 75.40.Cx, 75.50.Ee, 75.30.Gw, 75.30.Et, 75.30.Kz