Local spin spirals in the Neel phase of La_{2-x}Sr_xCuO_4

TL;DR

This paper models the magnetic properties of lightly doped La_{2-x}Sr_xCuO_4 using a spiral solution of the t-t'-t''-J model, explaining incommensurate ordering, neutron scattering peaks, spin-wave gap, and susceptibility variations.

Contribution

It introduces a spiral solution of the t-t'-t''-J model that accounts for experimental magnetic phenomena in lightly doped La_{2-x}Sr_xCuO_4.

Findings

Explains the direction of incommensurate magnetic structure along the orthorhombic b-axis.

Calculates the positions and shapes of neutron scattering peaks.

Shows doping dependence of the spin-wave gap and susceptibility.

Abstract

Experimental observations of lightly doped La_{2-x}Sr_xCuO_4, x < 0.02, revealed remarkable magnetic properties such as the incommensurate noncollinear ordering (additional to the Neel ordering) and a tremendous doping dependence of the uniform longitudinal susceptibility. We show that the spiral solution of the t-t'-t''-J model obtained by taking into account the Coulomb trapping of holes by Sr ions describes these puzzling data perfectly well. Our solution firstly explains why the incommensurate structure is directed along the orthorhombic b-axis, and secondly allows a numerical calculation of the positions and shapes of the incommensurate neutron scattering peaks. Thirdly, we calculate the doping dependence of the spin-wave gap, and lastly, we study the longitudinal magnetic susceptibility and show that its doping dependence is due to the noncollinearity of the spin spiral.