Magnetoresistance of CoFeNi/Cu Superlattices Differing in the Ferromagnetic Alloy Composition

The structure and magnetoresistive properties of Ta(5 nm)/NiFeCr(5 nm)/[FM(t(FM))/Cu(2.2 nm)](n)/ Ta(5 nm) superlattices prepared by magnetron sputtering are studied in this work. The ferromagnetic layer thickness t(FM) is varied in a 1.1-1.5 nm range. The Co90Fe10, Co85Fe12Ni3, Co77Fe17Ni6, and Co70Fe20Ni10 alloys with an fcc structure and close saturation magnetization values are used as the ferromagnetic (FM) materials. It is shown that, as the Ni and Fe contents in the CoFeNi alloy increase, the magnetoresistance of superlattices containing eight bilayers remains high and equal to 24-28%; in this case, the twofold decrease in the hysteresis occurs. As the number of bilayers in the superlattices, which contain CoFeNi alloys differing in composition increases to 12, the close values of magnetoresistance 30-31% are obtained. The correlation between the saturation magnetization of the ferromagnetic material of superlattice layers and maximum value of magnetoresistance is discussed.