Magnetic structure and spin waves in the frustrated ferro-antiferromagnet Pb2VO(PO4)2

Abstract

Single crystal neutron diffraction, inelastic neutron scattering and electron spin resonance experiments are used to study the magnetic structure and spin waves in Pb2VO(PO4)2, a prototypical layered S = 1/2 ferromagnet with frustrating next nearest neighbor antiferromagnetic interactions. The observed excitation spectrum is found to be inconsistent with a simple square lattice model previously proposed for this material. At least four distinct exchange coupling constants are required to reproduce the measured spin wave dispersion. The degree of magnetic frustration is correspondingly revised and found to be substantially smaller than in all previous estimates.arXiv :1902.11172v2 [cond-mat.str-el]

Realizing square and diamond lattice S=1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, Abdeldaim1, Li2, Farrar3 et al. 2020Phys. Rev. Materials

“…2(c) and can be described as a G-type antiferromagnet with the magnetic moments aligned along the c axis. The twodimensional character of α-KTi(C 2 O 4 ) 2 •x D 2 O is corroborated by the observed ordered moment µ = 0.62(3) µ B per Ti 3+ extracted from the Rietveld fit, similar to other square network systems [5,70,71], and to the expected ordered moment of 0.6 µ B for a S = 1/2 square lattice antiferromagnet [72][73][74]. The discrepancy between the value extracted from the fit to PND data and the expected gSµ B = 0.81 µ B extracted from the HTE fit is most likely associated with data renormalization issues as discussed in Sec.…”

Presaturation phase with no dipolar order in a quantum ferro-antiferromagnet

“…61) structure with 8 V 4+ ions per unit cell [13] forming an approximate S = 1/2 square lattice in the (a, b) plane. If what is known about the structurally similar Pb 2 VO(PO 4 ) 2 is any guidance [14], magnetic interactions are in the these planes, with negligible inter-layer coupling. The nn and nnn in-plane exchange constants for BaCdVO(PO 4 ) 2 have been previously estimated from powder data as J 1 = −0.31 and J 2 = 0.28 meV [15].…”

Phase diagram and spin waves in the frustrated ferro-antiferromagnet SrZnVO(PO4)2

“…All the information available to date is consistent with it being a quantum spin-nematic. In contrast, quantum fluctuations in Pb 2 VO(PO 4 ) 2 are much weaker, the zero-field ordered moment is quite large [14], and the presaturation phase is very narrow [10]. Whether it lies above single-magnon condensation field is yet unclear.…”

“…Of the three vanadyl phosphates mentioned here, SrZnVO(PO 4 ) 2 appears to be the simplest one in terms of structure and the number of distinct magnetic interactions. Magnetic coupling between layers is assumed to be negligible, based on the previous direct measurements in Pb 2 VO(PO 4 ) 2 [14].…”