Abstract: Tunnel junctions are used to detect magnetic domains, such as bubble domains, using the change in Fermi level of one (or both) electrodes due to the magnetic field of the domain. The Fermi level shift causes the tunnel barrier height to change, leading to a change in tunneling conductance which is detectable as a current or voltage change. A simple tunnel junction in flux coupling proximity to the magnetic domains is suitable, but more sensitive detectors are made using Schottky barrier junctions, and magnetic semiconductors which exhibit conduction band splitting due to the stray field of the domains. In another embodiment, the magnetic sheet supporting the domains provides the tunnel barrier for sensing of the domains within it. Detection of submicron domains is easily achieved.