Hard Bias Effect on Magnetic Noise in Different Types of Tunnel Magnetoresistive Heads

Hard bias effect on thermally activated magnetic noise has been investigated through changing the biasing direction in three types of tunnel magnetoresistive (TMR) heads with different head structures and sensor widths. It is found that characteristic variation in the noise spectra is different for different TMR heads. The results can be explained through stiffness field difference in different TMR heads. No additional ferromagnetic resonance (FMR) was observed in accompanying with the hard bias weakness. The resonant frequency as a function of field at different bias angles can be qualitatively accounted for by relevant stiffness field variations.