Characterization of Superconductor Magnetic Properties in Crossed Magnetic Fields

This chapter deals with the characterization of the magnetic properties of superconductors which are subjected to magnetic fields that have been applied along two orthogonal directions, which is commonly referred to as a “crossed” magnetic field configuration. In a classical electromagnetism context, the term “crossed” field may sound puzzling since it is learned from textbooks that field lines are locally parallel to the field vectors, hence they cannot cross. The term “crossed” refers rather to the sets of fields that have been applied to the sample, either sequentially, i.e., the superconductor is magnetized by applying and removing a field along one direction and then the material is subsequently subjected to a field along another direction, or simultaneously, i.e., two orthogonal external fields are applied, often with a time delay between them or with different characteristics, e.g., one is a DC field and the other is an AC field. Depending on the field characteristics, these configurations correspond in reality to a kind of rotation or periodic tilting of the applied field, but the somewhat artificial separation between what happens along two orthogonal directions proves often extremely helpful in understanding the observed phenomena. Hereafter, we will therefore omit quotation marks when using the terms crossed field, crossed flow or crossed flux. One can equivalently talk of mutually perpendicular fields or orthogonal fields.