Dependence of Current and Magnetic Field on Spin Transfer Induced Noise in CPP-GMR read Heads

This paper aims to investigate the magnetic noise dependence on the sense current, Isense, and the hard bias field, HB, of the current perpendicular to the plane giant magnetoresistance read heads. The macrospin modeling was performed in the simulations. The magnetic noise was examined by using power spectral density analysis. The results showed that the magnetic noise was increased with increasing Isense due to an enhancement of STT effect, especially a rapid increase of the noise was found when Isense exceeds a critical value. An asymmetry of Isense indicated that a negative current produces lower noise than a positive current since a ferromagnetic exchange coupling was existed in the model. In addition, the noise could be reduced by increasing HB which further results in an increase of the ferromagnetic resonance frequency. Hence, an optimization of Isense and HB strongly influences the magnetic noise and becomes an important factor for acheiving the high performance magnetic read head for higher recording densities.