Gapped ground state in the zigzag pseudospin-1/2 quantum antiferromagnetic chain compound PrTiNbO6

TL;DR

This study investigates the magnetic properties of PrTiNbO6, a rare-earth compound that realizes a zigzag pseudospin-1/2 quantum antiferromagnetic chain, revealing a gapped ground state due to anisotropy effects.

Contribution

It provides experimental evidence of a gapped ground state in a pseudospin-1/2 antiferromagnetic chain compound caused by off-diagonal anisotropy terms.

Findings

No magnetic freezing down to 0.1 K

Approximately 1 K energy gap observed at low temperatures

Ground state approaches zero residual spin entropy

Abstract

We report a single-crystal study on the magnetism of the rare-earth compound PrTiNbO$_6$ that experimentally realizes the zigzag pseudospin-$\frac{1}{2}$ quantum antiferromagnetic chain model. Random crystal electric field caused by the site mixing between non-magnetic Ti$^{4+}$ and Nb$^{5+}$, results in the non-Kramers ground state quasi-doublet of Pr$^{3+}$ with the effective pseudospin-$\frac{1}{2}$ Ising moment. Despite the antiferromagnetic intersite coupling of about 4 K, no magnetic freezing is detected down to 0.1 K, whilst the system approaches its ground state with almost zero residual spin entropy. At low temperatures, a sizable gap of about 1 K is observed in zero field. We ascribe this gap to off-diagonal anisotropy terms in the pseudospin Hamiltonian, and argue that rare-earth oxides open an interesting venue for studying magnetism of quantum spin chains.