Quantum disordered ground state and relative proximity to an exactly solvable model in the frustrated magnet CeMgAl${}_{11}$O${}_{19}$

Abstract

The magnetic properties of the triangular magnet CeMgAl${}_{11}$O${}_{19}$ were investigated by magnetization and specific heat measurements down to $T=0.03$K on single crystals grown by the floating zone method. The formation of effective spins $S_{\mathrm{eff}}=1/2$ below $T<10$\,K was confirmed both by DFT calculations and specific heat measurements. No magnetic order was found down to $T=0.03$K despite the formation of magnetic correlations observed in specific heat. The measured magnetization was compared with DMRG computation and their agreement supports the proposal of a strongly anisotropic magnetic interaction antiferromagnetically coupling the spin components in the $ab$ plane and ferromagnetically coupling the spin component along the $c$ axis. However, our quantitative study of the magnetization indicates a weaker proximity to quantum criticality between ferromagnetism and antiferromagnetism than the previous inelastic neutron scattering study. Finally, we propose that the absence of magnetic order in CeMgAl${}_{11}$O${}_{19}$ would most probably be related to the structural disorder revealed by single-crystal X-ray diffraction.

7 pages, 4 figures, 8 supplimentary materials pages, 5 supplimentary materials figures