Ultrasensitive Ferromagnetic Gyroscopes for Tests of Fundamental Physics

Under conditions where the total angular momentum of a ferromagnet is dominated by intrinsic spin, the ferromagnet will behave as a gyroscope. If such a ferromagnetic gyroscope (FG) can be sufficiently isolated from the environment, it can measure spin-dependent interactions with a sensitivity beyond that of any other known system. We discuss experimental progress toward realization of an FG and recent proposals to use levitated FGs to search for new interactions and investigate physics at the intersection between quantum mechanics and general relativity