Hysteresis reduction in NiFeCo/Cu multilayers exhibiting large low-field giant magnetoresistance

Giant magnetoresistance (GMR) has been observed in Ni66Fe16Co18/Cu multilayered uniaxial magnetic thin films prepared by dc magnetron sputtering. Both easy and hard axis loops saturate at very low applied fields. The MR ratio reaches ∼80% of its saturation value in less than 30 Oe. A maximum MR ratio of ∼10% has been observed in the as-deposited state in a structure containing only ten bilayers. Typical hysteresis values for magnetoresistance loops are ∼4 Oe in the as-deposited state. A gradual decrease of this hysteresis has been observed with annealing. An increase in the saturation field is also observed with annealing. Short-term annealing increases the magnitude of the magnetoresistance ratio; prolonged annealing causes a decrease. A field sensitivity of about 0.3% per Oe has been observed and dc magnetoresistance minor loops exhibit no measurable decrease in sensitivity.