Properties of spin 1/2 triangular lattice antiferromagnets: CuRE2Ge2O8 (RE=Y, La)

TL;DR

This study introduces CuRE2Ge2O8 (RE=Y, La) as new 2D quantum antiferromagnets with triangular lattices, exhibiting low-temperature magnetic order and field-induced phase transitions, supported by experimental and theoretical analyses.

Contribution

It reports the discovery and characterization of CuRE2Ge2O8 as a new class of low-dimensional quantum spin triangular antiferromagnets with detailed experimental and DFT analysis.

Findings

Long-range magnetic order at sub-Kelvin temperatures.

Presence of field-induced phase transitions.

Identification of the materials as charge-transfer insulators.

Abstract

We found new two-dimensional (2D) quantum (S=1/2) antiferromagnetic systems: CuRE2Ge2O8 (RE=Y and La). According to our analysis of high-resolution X-ray and neutron diffraction experiments, the Cu-network of CuRE2Ge2O8 (RE=Y and La) exhibits a 2D triangular lattice linked via weak bonds along the perpendicular b-axis. Our bulk characterizations from 0.08 to 400 K show that they undergo a long-range order at 0.51(1) and 1.09(4) K for the Y and La systems, respectively. Interestingly, they also exhibit field induced phase transitions. For theoretical understanding, we carried out the density functional theory (DFT) band calculations to find that they are typical charge-transfer-type insulators with a gap of Eg = 2 eV. Taken together, our observations make CuRE2Ge2O8 (RE=Y and La) additional examples of low-dimensional quantum spin triangular antiferromagnets with the low-temperature magnetic ordering.