Structural and magnetic characterization of CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$ with two-dimensional pseudospin-1/2 triangular lattice

TL;DR

This study characterizes the structural and magnetic properties of CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$, revealing their potential as quantum spin liquid candidates or for refrigeration applications due to their weak exchange interactions.

Contribution

It provides the first detailed structural and magnetic analysis of CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$, expanding the family of rare-earth heptatantalates studied for quantum magnetism.

Findings

CeTa$_7$O$_{19}$ is a highly anisotropic Ising triangular-lattice antiferromagnet.

YbTa$_7$O$_{19}$ exhibits in-plane magnetic anisotropy similar to YbMgGaO$_4$.

Both compounds have weak exchange interactions, making them potential quantum spin liquid candidates or for refrigeration.

Abstract

Triangular lattice antiferromagnets are prototypes for frustrated magnetism and may potentially realize novel quantum magnetic states such as a quantum spin liquid ground state. A recent work suggests NdTa$_7$O$_{19}$ with rare-earth triangular lattice is a quantum spin liquid candidate and highlights the large family of rare-earth heptatantalates as a framework for quantum magnetism investigation. In this paper, we report the structural and magnetic characterization of CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$. Both compounds are isostructural to NdTa$_7$O$_{19}$ with no detectable structural disorder. For CeTa$_7$O$_{19}$, the crystal field energy levels and parameters are determined by inelastic neutron scattering measurements. Based on the crystal field result, the magnetic susceptibility data could be well fitted and explained, which reveals that CeTa$_7$O$_{19}$ is a highly anisotropic Ising triangular-lattice antiferromagnet ($g_z$/$g_{xy}$$\sim$3) with very weak exchange interaction (J$\sim$0.22~K). For YbTa$_7$O$_{19}$, millimeter sized single crystals could be grown. The anisotropic magnetization and electron spin resonance data show that YbTa$_7$O$_{19}$ has a contrasting in-plane magnetic anisotropy with $g_z$/$g_{xy}$$\sim$0.67 similar as that of YbMgGaO$_4$. The above results indicate that CeTa$_7$O$_{19}$ and YbTa$_7$O$_{19}$ with pseudospin-1/2 ground states might either be quantum spin liquid candidate materials or find applications in adiabatic demagnetization refrigeration due to the weak exchange interaction.