High-pressure synthesis of quantum magnet M-YbTaO4 with a stretched diamond lattice

TL;DR

This study reports the high-pressure synthesis of a quantum magnet M-YbTaO4 with a stretched diamond lattice, revealing no long-range magnetic order down to 1.8 K and demonstrating the stabilization of a solid solution in the M phase.

Contribution

It introduces a high-pressure synthesis method for M-YbTaO4 and YbNbxTa1-xO4, enabling stabilization of the M phase and exploring its magnetic properties.

Findings

No long-range magnetic order observed down to 1.8 K

High-pressure synthesis stabilizes the M phase for the entire solid solution

Magnetic properties show little variation with composition or annealing

Abstract

We report bulk magnetic properties of ytterbium tantalate in its monoclinic fergusonite modification, M-YbTaO4. The spin-1/2 Yb3+ ions in this phase are arranged on a geometrically frustrated "stretched diamond" lattice. M-YbTaO4 cannot be prepared at ambient pressure and was instead prepared in a belt-type apparatus at 6 GPa and 1800 C. Susceptibility and specific heat data show no long-range ordering down to 1.8 K and are consistent with a Jeff = 1/2 Kramers doublet which splits in an applied field. Furthermore, under high-pressure synthesis the entire solid solution YbNbxTa1-xO4 (0 < x < 1) can be stabilised in the M phase, in contrast to ambient-pressure synthesis which favours the competing M' phase for Ta-rich compositions. Subsequent annealing of the Nb-Ta mixed samples resulted in colour changes, suggesting oxygen deficiency in some of the as-prepared high pressure samples. There was little variation in the bulk magnetic properties upon varying either the Nb/Ta ratio or the annealing conditions.