Experimental Observation of the1/3Magnetization Plateau in the Diamond-Chain CompoundCu3(CO3)2

Abstract

The magnetic susceptibility, high field magnetization, and specific heat measurements of Cu3(CO3)2(OH)2, which is a model substance for the frustrating diamond spin chain model, have been performed using single crystals. Two broad peaks are observed at around 20 and 5 K in both magnetic susceptibility and specific heat results. The magnetization curve has a clear plateau at one third of the saturation magnetization. The experimental results are examined in terms of theoretical expectations based on exact diagonalization and density matrix renormalization group methods. An origin of magnetic anisotropy is also discussed.

Magnetoelastic couplings in the distorted diamond-chain compound azurite

“…Among these systems, the diamond chain has been of particular interest, where triangular arrangements of spin S = 1/2 entities with exchange coupling constants J 1 , J 2 , and J 3 are connected to form chains [1][2][3][4]. In recent years, great interest has surrounded the discovery of azurite, Cu 3 (CO 3 ) 2 (OH) 2 [5], as a model system of a Cu 2+ (S = 1/2)-based distorted diamond chain with J 1 = J 2 =J 3 [9]. The observation of a plateau at 1/3 of the saturation magnetization [9] is consistent with a description of azurite in terms of an alternating dimer-monomer model [2,10].…”

“…In recent years, great interest has surrounded the discovery of azurite, Cu 3 (CO 3 ) 2 (OH) 2 [5], as a model system of a Cu 2+ (S = 1/2)-based distorted diamond chain with J 1 = J 2 =J 3 [9]. The observation of a plateau at 1/3 of the saturation magnetization [9] is consistent with a description of azurite in terms of an alternating dimer-monomer model [2,10]. Two characteristic temperatures (energies) have been derived from peaks in the magnetic susceptibility χ (T ) [9,10].…”

High-resolution thermal expansion measurements under helium-gas pressure

“…The performance of the apparatus described here is demonstrated by dilatometric measurements both at ambient pressure and P = 104 MPa on the natural mineral azurite, Cu 3 (CO 3 ) 2 (OH) 2 , a quasi-one-dimensional spin S = 1/2 Heisenberg antiferromagnet -a good realization of a distorted diamond chain. 18 The expansivity data demonstrate a significant effect of pressure, indicating a strong pressure dependence of the magnetic interactions in this system.…”

“…This material has attracted considerable interest recently due to the discovery of a plateau in the low-temperature magnetization at 1/3 of the saturation magnetization. 18 The crystal studied here stems from the same large single crystal explored in Ref. 32.…”

“…The ambientpressure results, which coincide with published data, [32][33][34] reveal three distinct anomalies, seen also in magnetic susceptibility data, which can be assigned to characteristic energy scales of azurite. 18 The rounded peak anomaly around 20 K marks the formation of spin singlet S dimer = 0 dimers, involving two thirds of the material's Cu 2 + S = 1/2 spins. The corresponding antiferromagnetic intra-dimer exchange coupling J 2 /k B 33 K represents the dominant magnetic energy scale of the system.…”