The present invention relates to control of synchronous machines. The stabilizer is pivotable into a retraction position within the casing. The air is pushed through a particulate filter in the air channel and then through at least one aperture into the head space. After that, supercritical carbon dioxide is gasified. The second content may contain interference information. The ferromagnetic end regions of the bias layer are antiferromagnetically coupled across the APC layer to the corresponding underlying free layer end regions to provide the longitudinal biasing.