The Evolution of the Antiferromagnetic Order with Hole Doping of La2-xSrxCoO4.

Many believe that the magnetic excitations of cuprate high temperature superconductors play an important role in the material's superconductivity. Understanding the magnetic excitation spectrum of La2-xSrxCoO4 could provide a breakthrough in understanding cuprate superconductors, as both materials have very similar magnetic excitations. The electric charges that are doped into the Co-O layers La2-xSrxCoO4 by replacing La with Sr, either form regularly spaced lines; charge-stripes, or a pattern like a chess/checkerboard; checkerboard order. There are insufficient charges doped into the material to form these charge orders, leaving pockets of the material that should be equivalent to undoped La2CoO4, however an energy gap seen in the magnetic excitations of La2CoO4 is not observed. We will study the magnetic excitations at very low doping to see how this energy gap evolves with doping.