Magnetic structure ofLi2CuO2: Fromab initiocalculations to macroscopic simulations

Abstract

The magnetic structure of the edge-sharing cuprate compound Li 2 CuO 2 has been investigated with highly correlated ab initio electronic structure calculations. The first-and second-neighbor in-chain magnetic interactions are calculated to be 142 and Ϫ22 K, respectively. The ratio between the two parameters is smaller than suggested previously in the literature. The interchain interactions are antiferromagnetic in nature and of the order of a few K only. Monte Carlo simulations using the ab initio parameters to define the spin model Hamiltonian result in a Néel temperature in good agreement with experiment. Spin population analysis situates the magnetic moment on the copper and oxygen ions between the completely localized picture derived from experiment and the more delocalized picture based on local-density calculations.

Low-dimensional magnetism of spin-½ chain systems of α- and β-TeVO4: A comparative study

“…5,6 the dependence of the magnetic interactions on the Me-O-Me angle was analyzed. According to de Graaf et al [6], the angle at which FM exchange interaction reaches its maximum is close to 97°, while the critical angle at which the exchange interaction changes its sign from FM to AFM is close to 104°. From geometrical considerations, it can be expected that the NN exchange interactions in α-TeVO 4 have different magnitudes (and possibly signs) due to the difference in V-V distances and V-O-V angles.…”

Magnetoelectricity in the ferrimagnetic Cu2OSeO3: symmetry analysis and Raman scattering study

“…A close inspection of distances and angles leads to the conclusion that we deal with the following type of exchange integrals: Here, ferromagnetic exchange 0 F J < and antiferromagnetic exchange 0 AF J > , in the parenthesizes the oxygen ions are shown trough which the magnetic bonds are realized, the Cu-Cu distances are given in the braces. Note that there is no consensus about the critical angles of Cu-O-Cu magnetic bonds at which magnetic exchange changes sign ( [12,13], and discussion in [14]). Therefore, our attribution of CuI-CuII (3.049 Å) exchange to the ferromagnetic one has to be confirmed by further calculations.…”

“…1) closeness almost of all Cu-O-Cu bond angles to 90º, which results to the appearance of ferromagnetic exchange interactions [12,13];…”

Temperature-dependent optical conductivity of undoped cuprates with weak exchange

“…This will cause a strong T -dependence of various response functions, here presented for the case of the optical conductivity σ(ω). For an illustration of our approach we consider Li 2 CuO 2 being of current interest 1,2,3,4,5,6,7,8,9,10,11,12 , structurally simple, and most importantly, where single crystal data are available in a broad ω-range 1,2 . This system stands for a class of frustrated spin-1/2 chain materials with both small ferromagnetic (FM) NN Cu-Cu exchange coupling J 1 and AFM next-nearest neighbor (NNN) Cu-Cu in-chain exchange J 2 1,3 in terms of a 1D spin-1/2 Heisenberg model…”