Amplitude and Phase Distributions of Magnetization in Tunneling Magnetoresistive Heads

We describe a thermal magnetic noise simulation of tunneling magnetoresistive (TMR) heads. We calculate the phase and amplitude distributions of the local noise resistance derived from the magnetization fluctuation of the free layer in the several gigahertz range and consider their relations with the magnetic noise spectrum. The results show that the phase distribution of the noise resistance strongly influences the second or higher resonant peaks in the magnetic noise spectrum of TMR heads. As an example, we show that the second resonant peak appears in the spectrum when the asymmetric magnetic field is applied to the free layer.