Giant magnetoresistance in soft magnetic NiFeCo/Cu multilayers

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Abstract
Giant magnetoresistance effect and crystal structure have been investigated for Ni66Fe16Co18/Cu multilayers with Fe and NiFeCo buffer layers prepared by rf magnetron sputtering. For both buffer layers, the multilayers show magnetoresistance, which oscillates as a function of Cu thickness. The maximum magnetoresistance ratios at the first peak are 35% and 25% and those at the second peak are 15% and 12% for the Fe and NiFeCo buffer layers, respectively. The multilayers with the NiFeCo buffer show weaker antiferromagnetic coupling than those with the Fe buffer. The NiFeCo (5 nm) [NiFeCo(1.5 nm)/Cu(2.2 nm)]30 multilayer with uniaxial magnetic anisotropy shows a MR ratio of 12%, which reaches 90% of the saturation with a field as low as 20 and 30 Oe in the easy and hard directions, respectively.