Models of microwave-assisted magnetic recording are used to investigate the potential of the technology. With both single- and double-layer [exchange coupled composite (ECC)] media, the higher effective head field gradient led to reduced transition jitter and higher SNR in written tracks. To reduce the high-frequency field to a realistic frequency range, the use of ECC media is required. However, the ECC medium design must consider interactions between the spin torque oscillator and the medium.