Unconventional spin freezing in the highly two-dimensional spin-12kagome antiferromagnetCd2Cu3(OH)6(SO4

Abstract

S = 1/2 quantum-spin systems of the kagome lattice have received intense recent attention because they are expected to be promising candidates for novel quantum states such as spin liquid, spin nematic, and other unknown exotic states. Here we report an unusual transition in a highly two-dimensional and slightly distorted S = 1/2 quantum kagome system Cd 2 Cu 3 (OH) 6 (SO 4 ) 2 4H 2 O, which is a purified compound of the recently identified mineral edwardsite, Cd 1.89 Zn 0.11 Cu 3 (OH) 6 (SO 4 ) 2 4H 2 O. The S = 1/2 spins of Cu 2+ ions form a highly two-dimensional kagome lattice with an extraordinarily large interlayer spacing >10Å, thus providing a unique kagome lattice with minimum interlayer perturbation. The magnetization shows a Curie-Weiss temperature of 40.5 K and moment freezing below around T F = 5 K and a magnetic transition feature near 3 K. The muon spin relaxation shows static magnetism below 5 K and saturation below 3 K. However, distinct features have been observed distinguishing it from a spin glass or a conventional order: High-field magnetization until 50 T showed a saturated value of only 1/3 of the full expected moment. Analysis of specific heat suggests that only 1/3 of the spins are related to the magnetic order; on the other hand, the order is destroyed in external field and 1/3 of the spins respond to the field with a Schottky-like behavior while the other 2/3 of the spins remain inactive. These experimental results suggest an unconventional coexistence of the partial order and most probably spin singlets.

Magnetization plateaus in the spin- 12 antiferromagnetic Heisenberg model on a kagome-strip chain

“…Our study reveals that there are a number of magnetization plateaus even with three different exchange interactions in the kagome-strip chain. It thus suggests that magnetization plateaus appear not only in a perfect kagome lattice [22] but even in distorted kagome lattices [23][24][25][26][27][28][29][30][31][32][33]. In fact, a 1/3 plateau confirmed in Cs 2 Cu 3 CeF 12 [33] corresponds to the 1/5 plateaus, B and I, in the kagome-strip chain.…”

Magnetic Phase Diagrams and Magnetization Plateaus of the Spin-1/2 Antiferromagnetic Heisenberg Model on a Square-Kagome Lattice with Three Nonequivalent Exchange Interactions

“…This is because of the difficulty in synthesizing compounds that fit to theoretical models. In particular, many compounds exhibit lattice distortions that do not correspond to theoretical models [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. It is thus important to theoretically study lattices with distortions to make comparison easy with real compounds.…”

The long-range magnetic order and underlying spin model in shattuckite Cu5(SiO3)4(OH)2

“…Recently, efforts in this field were directed to studies and elucidation of quantum ground states in dimer compounds callaghanite Cu 2 Mg 2 (CO 3 )(OH) 6 2H 2 O (Lebernegg et al 2014) and urusovite CuAlAsO 5 (Vasiliev et al 2015), frustrated spin-chain linarite PbCuSO 4 (OH) 2 (Schäpers et al 2014) and quasi-two-dimensional diaboleite Pb 2 Cu(OH) 4 Cl 2 (Tsirlin et al 2013). The edwardsite Cd 2 Cu 3 (OH) 6 (SO 4 ) 2 4H 2 O (Fujihala et al 2014) presents evidence of partial order and coexisting spin singlet state on a distorted kagome lattice, while francisite Cu 3 Y(SeO 3 ) 2 O 2 Cl (Zakharov et al 2014) realizes exotic three-sublattice non-collinear antiferromagnetic structure at low temperatures. Here, we present another copper-based mineral shattuckite Cu 5 (SiO 3 ) 4 (OH) 2 where the ions of divalent copper constitute unique combination of well-separated chains and two-dimensional patterns.…”