Effect of FGL Cone Angle on Recording Performance in Microwave-Assisted Magnetic Recording

Microwave-assisted magnetic recording (MAMR) uses the field from a spin torque oscillator (STO) to assist the switching of recording medium magnetization. In an ideal STO, the magnetization of the field generating layer (FGL) would rotate in the plane of the FGL. In practice, the FGL magnetization usually has an out-of-plane component and the FGL magnetization vector describes a cone as it rotates. The cone angle θ
_c
is the angle between the FGL magnetization and the axis normal to the plane of the FGL. This article investigates the effect of the cone angle on the recording performance and compares two types of recording media: notched and exchange-coupled composite. The results show that for FGL cone angles between 45° and 90°, the recording performance was mainly determined by the strength of the high-frequency magnetic field from the FGL. For smaller cone angles, the signal-to-noise ratio (SNR) rapidly decreased.