Quasi-two-dimensional spin-1/2 magnetism in α-TeVO4

Y. Zhao¹, J. A. Rodriguez^{2, 3}, P. Lemmens⁴, H. Berger⁵, and C. Broholm ^{1, 3, 6}

1Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA

2Department of Materials Science and Engineering, University of Maryland, College Park, MD, USA

3NIST Center for Neutron Research, Gaithersburg, Maryland, 20899, USA

4Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany

5Inst. Phys. Mat. Complexe, EPFL, CH-1015 Lausanne, Switzerland

6Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA

α -TeVO4 is a monoclinic structure where four spin-1/2 V⁴⁺ ions per unit cell form chain-like structures extending along the b-axis. Using the new MACS spectrometer at the NIST Center for Neutron Research, we have carried out a comprehensive investigation of magnetism in this compound. The phase transition at T_C = 16 K is to long range order that can be described as ferromagnetic planes stacked anti-ferromagnetically along the (1, 0, -2) direction. Powder diffraction indicates moments oriented along b-axis with a magnitude of 0.81(3) µ_B at T=1.4 K. The inelastic scattering data reveal a strongly anisotropic magnon dispersion relation which is almost independent of wave vector transfer along (1, 0, -2) at high energies.