Time domain analysis of low frequency noise in giant magneto-resistive recording heads

The low frequency noise observed in giant magnetoresistive recording heads was studied in the time domain, Time series data was collected on bottom sp in-valve sensors while varying the bias current (I-b) about a nominal opera ting point. An optimal time delay of 5 ns was chosen based on a 80% reducti on in mutual information. Two dimensional embedding of the data revealed a progression from one stable state for low I-b to two metastable states and finally a second stable state at high I-b. The metastable states manifest t hemselves as random telegraphic noise in the time series. The average time between noise spikes was obtained by calculating the time between consecuti ve points on a Poincare section and was estimated as 0.37 mus. The Renyi en tropy was used to quantify the stability of the system both with and withou t an isolated pulse pattern.