Magnetic Phase Diagram of the Triangular Antiferromagnetic Cs₂CuCl_4−xBr_x Mixed System

Abstract

The novel magnetic phase diagram of the Cs 2 CuCl 4−x Br x mixed system is established by means of single crystal neutron diffraction in the lowest temperature region and zero magnetic field. Two long-range ordered magnetic phases exist in this mixed system depending on the Cl/Br concentration. In the rich Cl concentration range, the ordered magnetic state occurs below the ordering temperature T N = 0.51(1) K for Cs 2 CuCl 3 Br 1 and at Cs 2 CuCl 2.6 Br 1.4 below T N = 0.24(2) K. Magnetic order with a temperature-independent position (0, 0.573(1), 0) below the ordering temperature T N = 0.63(1) K appears in the rich Br concentration for Cs 2 CuCl 0.6 Br 3.4 . Between the rich Cl and rich Br concentration ranges (two magnetic phases), there is a range of x without magnetic order down to 50 mK. A suggestion about the magnetic exchange paths in the bc-layer for different regimes is presented, which can be controlled depending on the preferred Br occupation in the [CuX 4 ] tetrahedra. The density functional theory calculations of the exchange coupling constants J, J for some ordered compositions of the mixed system Cs 2 CuCl 4−x Br x indicate that these are not frustrated.

Spin excitations in the frustrated triangular lattice antiferromagnet NaYbO$_2$

“…In particular, the search for conditions that realize ground states disordered by quantum fluctuations remains of sustained interest, with proposed phases ranging from "resonating valence bond" states [3,4,13], to quantum dimer phases [14][15][16], to a variety of spin liquid phases [17][18][19][20][21][22][23][24][25], some of which may realize longrange entanglement. However, finding pristine material systems to match many of these models remains an outstanding challenge, as effects in real materials such as orbital ordering [26][27][28], Jahn-Teller distortions [29,30], anisotropic exchange [31][32][33][34], and exchange disorder [35][36][37][38] can either induce order, quench the moments entirely, or reduce the dimensionality to quasi-1D.…”

Pressure-tuning the quantum spin Hamiltonian of the triangular lattice antiferromagnet Cs2CuCl4

“…2 and references therein), the two compounds, Cs 2 CuCl 4 and Cs 2 CuBr 4 (with J ′/ J ≃ 0.30 and 0.41, respectively 6 ), remain among the most prominent representatives of this family of frustrated materials. One obvious approach to tune the spin Hamiltonian of these systems is to vary their chemical composition 7,8 . However, experiments on the solid solution Cs 2 CuCl 4− x Br x (with Br content ranging from 0 to 4) revealed a pronounced difference in the Cu coordination when increasing x , resulting in a discontinuous evolution of its crystal structure 9 .…”