Research: Pressure tuning of exchange couplings in a frustrated magnet

Spin-1/2 triangular-lattice Heisenberg antiferromagnets belong to one of the most important classes of frustrated quantum magnets. In spite of their simple magnetic structures, they possess highly unusual magnetic and thermodynamic properties. One major obstacle in this area of research is the lack of materials with appropriate, ideally tuned, magnetic parameters. Using Cs₂CuCl₄ as a model system, we demonstrate an alternative approach, where, instead of the chemical composition, the spin Hamiltonian is altered by hydrostatic pressure. Our approach combines high-pressure high-field electron spin resonance (ESR) and magnetization measurements. The results allowed us not only to quasi-continuously tune the exchange parameters, but also to accurately monitor them by measuring the pressure-dependent shift of the ESR lines. The application of a pressure of up to 2 GPa increases the exchange-coupling parameters in this compound by up to 70%, triggering a cascade of new low-temperature field-induced phase transitions, absent at zero pressure.

S. A. Zvyagin, D. Graf, T. Sakurai, S. Kimura, H. Nojiri, J. Wosnitza, H. Ohta, T. Ono, H. Tanaka,
Pressure-tuning the quantum spin Hamiltonian of the triangular lattice antiferromagnet Cs₂CuCl₄,
Nat. Commun. 10,1064 (2019) (arXiv)