• Lumsden, Mark D.
• Schlueter, J. A.
• Manson, J. L.
• Hong, Tao
• Dunmars, C.
• Tian, Wei
• Podlesnyak, Andrey A.
• Wang, Cuihuan
• Christianson, Andrew D.
• Cao, Huibo
• Fishman, Randy Scott
• Ehlers, Georg

Abstract

We have performed elastic and inelastic neutron scattering experiments on single crystal samples of the coordination polymer compound CuF{sub 2}(H{sub 2}O){sub 2}(pyz) (pyz = pyrazine) to study the magnetic structure and excitations. The elastic neutron diffraction measurements indicate a collinear antiferromagnetic structure with moments oriented along the [0.7 0 1] real-space direction and an ordered moment of 0.60 {+-} 0.03 {micro}B/Cu. This value is significantly smaller than the single-ion magnetic moment, reflecting the presence of strong quantum fluctuations. The spin wave dispersion from magnetic zone center to the zone boundary points (0.5 1.5 0) and (0.5 0 1.5) can be described by a two-dimensional Heisenberg model with a nearest-neighbor magnetic exchange constant J{sub 2D} = 0.934 {+-} 0.0025 meV. The interlayer interaction J{sub perp} in this compound is less than 1.5% of J{sub 2D}. The spin excitation energy at the (0.5 0.5 0.5) zone boundary point is reduced when compared to the (0.5 1 0.5) zone boundary point by {approx}10.3% {+-} 1.4%. This zone boundary dispersion is consistent with quantum Monte Carlo and series expansion calculations for the S=1/2 Heisenberg square lattice antiferromagnet, which include corrections for quantum fluctuations to linear spin wave theory.

Topics

• impedance spectroscopy
• dispersion
• compound
• polymer
• single crystal
• theory
• experiment
• laser emission spectroscopy
• neutron diffraction
• two-dimensional
• Inelastic neutron scattering