Tuning the S=1/2 square-lattice antiferromagnet Sr2Cu(T

Abstract

The spin-1/2 square-lattice Heisenberg model is predicted to have a quantum disordered ground state when magnetic frustration is maximized by competing nearest-neighbor J1 and next-nearest-neighbor J2 interactions (J2/J1 ≈ 0.5). The double perovskites Sr2CuTeO6 and Sr2CuWO6 are isostructural spin-1/2 square-lattice antiferromagnets with Néel (J1 dominates) and columnar (J2 dominates) magnetic order, respectively. Here we characterize the full isostructural solid solution series Sr2Cu(Te1-xWx)O6 (0 ≤ x ≤ 1) tunable from Néel order to quantum disorder to columnar order. A spin-liquid-like ground state was previously observed for the x = 0.5 phase, but we show that the magnetic order is suppressed below 1.5 K in a much wider region of x ≈ 0.1-0.6. This coincides with significant T-linear terms in the lowtemperature specific heat. However, density functional theory calculations predict most of the materials are not in the highly frustrated J2/J1 ≈ 0.5 region square-lattice Heisenberg model.Thus, a combination of both magnetic frustration and quenched disorder is the likely origin of the spin-liquid-like state in x = 0.5.

Site-Selective d10/d0 Substitution in an S = 1/2 Spin Ladder Ba2CuTe1–xWxO6 (0 ≤ x ≤ 0.3)

“…However, it appears formation of the Néel ordered state is suppressed to a lesser degree, with the γ-term for x = 0.3 approaching 50% of the value for Sr2CuTe0.5W0.5O6. 25 In line with the d 10 vs d 0 effect observed in double perovskites (i.e. W 6+ -strong J2; Te 6+ -strong J1), W 6+ is also expected to introduce a diagonal component to the intra-ladder interactions, effectively creating twists in the ladder where the W 6+ are located.…”

“…16,19,[21][22][23][24] Upon introducing a mixture of W 6+ and Te 6+ , the material evades ordering over a wide portion (x = 0.05 -0.6) of the Sr2CuTe1-xWxO6 solution. 7,10,[25][26][27][28] The 50:50 mixture Sr2CuTe0.5W0.5O6 closely resembles a quantum spin-liquid, an exotic magnetic state where the moments remain dynamic at zero Kelvin and have been highly sought since they were first proposed in the 1970s. [29][30][31][32] The question remains whether similarly exotic magnetic behavior can be introduced by d 10 /d 0 doping in other magnetic lattices than the square-lattice, and whether this can be extended from perovskites to perovskite-derived structures?…”

Exchange Interactions Mediated by Nonmagnetic Cations in Double Perovskites

“…Furthermore, the specific heat behavior at low temperatures is reminiscent of a gapless QSL state with collective excitations of entangled spins [11]. Fascinatingly, the suppression of long range magnetic order is observed in a wide region of x ≈ 0.1 − 0.6 [20].…”

Realizing square and diamond lattice S=1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, Abdeldaim1, Li2, Farrar3 et al. 2020Phys. Rev. Materials

“…Systems based on the S = 1/2 Heisenberg frustrated square lattice (FSL) model, for example, are extensively studied as they provide a rich magnetic phase diagram depending on the degree of frustration between exchange interactions along the sides, J 1 , and across the diagonal, J 2 , of the square net. For the antiferromagnetic phase diagram [4], theoretical predictions for the development of Néel and columnar antiferromagnetic orders within the respective dominant J 1 or J 2 regimes have been experimentally established in several materials [5][6][7][8][9][10][11][12][13]. Intriguingly, at the border of these * Email address: l.m.clark@bham.ac.uk two regimes, materials in which the degree of frustration is maximized-i.e.…”