A study on the dynamical spinsusceptibility of paramagnetic La2CuO4

The one electron wavefunctions and energy bands obtained by the self-consistent LMTO-ASA method in the local density approximation are used to calculate the wavevector and frequency dependent non-interacting spin susceptibility of paramagnetic La₂CuO₄ in thebct-structure. We show that matrix elements effects lead to a substantial depression of the susceptibility, especially for wavevectors near the X-point. Whereas interband transition contributions turn out to be significant, Fermi surface nesting properties are shown to be of less importance. In contradiction to the impression given by spin polarized electronic structure calculations the RPA-LDA approximation for the susceptibility predicts this substance to be far away from a magnetic phase transition, and we shed some light on the cause for this failure.