Abstract: A microwave circulator uses a thin-film exchange-coupled structure to provide an in-plane magnetic field around the circulator. The exchange-coupled structure is a ferromagnetic layer having an in-plane magnetization oriented generally around the circulator and an antiferromagnetic layer exchange-coupled with the ferromagnetic layer that provides an exchange-bias field to the ferromagnetic layer. A plurality of electrically conductive ports are connected to the exchange-coupled structure. Each of the portions or legs of the circulator between the ports may have an electrical coil wrapped around it with each coil connected to an electrical current source. The ferromagnetic resonance (FMR) frequency of the exchange-coupled structure in the absence of an external magnetic field is determined by the properties of the material of ferromagnetic layer and the magnitude of the exchange-bias field due to the exchange-coupling of the ferromagnetic layer to the antiferromagnetic layer.