Use of europium selenide films for magneto-optical studies at low temperatures

The resolution of the magneto-optical technique to observe directly the structure of the intermediate state in superconductors has been considerably improved by the replacement of EuS–EuF2 mixture by EuSe thin films with higher specific Faraday rotation. This allows a reduction of the magneto-optical film thickness, and consequently an enhancement of the optical and magnetic resolution. This greater rotation gives the possibility to work with the polarizers not completely crossed, and therefore to produce more luminous images. Theses images can directly be observed with a video camera so the rapidly changing structures can be recorded and flux tube velocities measured.