We theoretically analyze surface magnetoplasmon modes in a compact circular cavity made of magneto-optical material under a static magnetic field. Such a cavity provides two different physical mechanisms for the surface wave to circulate in a unidire
ctional manner around the cavity, which offers more freedom to realize one-way surface wave. We also show the interaction between this one-way cavity and waveguides, through an example of a circulator, which lays the fundamental groundwork for potential nonreciprocal devices.
