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

Abstract

We report a single-crystal study on the magnetism of the rare-earth compound PrTiNbO6 that experimentally realizes the zigzag pseudospin-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-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.

Partial Up-Up-Down Order with the Continuously Distributed Order Parameter in the Triangular Antiferromagnet TmMgGaO4

“…[10] for Yb x Lu 1−x MgGaO 4 ] . The small Curie-Weiss temperature is obtained by the fit to χ measured in the temperature range where S m ∼ Rln2, and thus the CEF effect due to excitations to higher CEF levels is negligible, and we obtain θ w = -3(J zz 1 + J zz 2 )/2 (see below) [11,39]. Therefore, the magnetic ions should be almost homogeneously distributed in both diluted samples, otherwise significant Curie-Weiss temperatures should be expected.…”

“…A similar effective spin-1/2 Ising Hamilitonian with a continuous distribution of the microscopic parameters can be applied to other non-Kramers rare-earth magnets with correlated GS quasidoublets, such as the Pr 3+ effective spin-1/2 chain compound, PrTiNbO 6 , with the similar site-mixing disorder between nonmagnetic Ti 4+ and Nb 5+ ions [39]. Therefore, the correlated magnetism of the GS quasidoublets should be general as well in condensed matter physics, as the structural disorder is usually inevitable in a real material.…”

“…The difference between the Kramers Yb 3+ and non-Kramers Tm 3+ cases is clearly seen in C m /T , where the signal of the diluted Yb 3+ sample diverges at low temperatures, whereas the diluted Tm 3+ sample reveals a finite zerotemperature value of C m /T . This finite value indicates a distribution of the energy splitting between the two lowest-lying CEF singlets, |E 1 and |E 2 [39]. This transforms two singlets into a quasidoublet and gives rise to the Ising anisotropy [38,39].…”

“…Between 30 and 60 K, S m is a constant of Rln2 [see Fig. 2 (e)], both the CEF excitations to higher levels and the intersite spin-spin correlations have marginal effect [39], and the mean-field approximation of the effective spin-1/2 system, χ = C /(T -θ w ), is applicable. Here, C = N A µ 0 µ 2 ef f /k B is the Curie constant, and the Curie-Weiss temperature of θ w = -3(J zz 1 + J zz 2 )/2 reflects the intersite magnetic couplings on the triangular lattice along the c axis (in the spin space) [11].…”

YbMgGaO4: A Triangular‐Lattice Quantum Spin Liquid Candidate

“…The very similar results were also reported in the kagome Ising antiferromagnet with even larger S m (0 K) ≈ 72.40% R ln2, and in the pyrochlore Ising ferromagnet with smaller S m (0 K) ≈ 29.25% R ln2, respectively. Further studies found the macroscopic GS degeneracy of a classical Ising system may be easily lifted by various kinds of perturbations, such as the second‐neighbor interaction and bond randomness, which are usually inevitable in a real material.…”