Competing exchange interactions in Li ₂ CuO ₂

Abstract

The dispersion of the spin-waves in single crystals of Li₂CuO₂ has been investigated by means of inelastic neutron scattering. The results yield a single spin-wave branch characterized by a large gap Δ = 1.4 meV at the zone centre due to easy-axis uniaxial anisotropy. Linear spin-wave theory is used to obtain the exchange integrals in this material. It turns out that the nearest-neighbor exchange interactions in the basal plane are antiferromagnetic leading to frustration between the magnetic moments. Our results show that Li₂CuO₂ is an <em>S</em> = 1/2 antiferromagnetic insulator with competing interactions.