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

TL;DR

This study investigates the magnetic properties of CeMgAl$_{11}$O$_{19}$, revealing a quantum disordered ground state with strong anisotropic interactions, and suggests structural disorder as a key factor preventing magnetic order.

Contribution

The paper provides detailed experimental and theoretical analysis of CeMgAl$_{11}$O$_{19}$, highlighting its quantum disordered state and proximity to an exactly solvable model, with insights into the role of structural disorder.

Findings

No magnetic order down to 0.03 K despite magnetic correlations.

Agreement between magnetization measurements and DMRG supports anisotropic magnetic interactions.

Structural disorder likely suppresses magnetic order in 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.