In this work we will investigate how the magnetic properties of nanometer thick iron-oxide films can be manipulated by heating them in air. Our preliminary results indicate that this can create remarkably large changes in the magnetic fields required to change the direction the film's magnetic moments point, increasing it by 100 % in some cases and decreasing it by 60 % in others. We will use polarised neutron scattering to try and understand these changes, with the ultimate aim of using these materials in novel devices.