Low temperature behaviour of the giant magnetoresistivity in CoFeB-SiOn granular composites

摘要

Giant magnetoresistivity (GMR) at different temperatures as well as magnetization processes were studied in amorphous granular composites (Co41Fe39B20)(x)(SiOn)(100-x) over a wide concentration range (20 less than or equal to x, at.% less than or equal to 59). Magnetoresistivity of the composites with large dielectric content (below a percolation threshold) is enhanced on cooling down to 77 K and reaches 7% in (Co41Fe39B20)(30)(SiOn)(70). The observed GMR enhancement directly correlates with the rise of the relative change of the composites magnetization ([m(77) - m(300)]/m(300)) occurring on temperature reduction. The temperature dependence of the composite's GMR exhibits a clear maximum in the vicinity of 77 K if a wider temperature range (2-300 K) is considered. The difference between the GMR values measured at 77 and 2 K is one order of magnitude. Strong Coulomb blockade is observed in this composite at low temperature. [References: 22]