Magnetoimpedance studies on urine treated Co66Ni7Si7B20 ribbons

Abstract

Magnetoimpedance (MI) response of Co66Ni7Si7B20 ribbons treated with artificial urine with protein bovine serum albumin (BSA), artificial urine without protein BSA and healthy male urine was studied as a function of time of incubation. The maximum MI [(MI)m] values of the ribbons treated with artificial urine without protein (RTAU) after 3h, 6h, 12h and 24h of incubation are 30% (at 4MHz), 15% (at 5MHz), 14% (at 10MHz) and 8% (at 13MHz) respectively. On the other hand, the respective (MI)m values of the ribbons treated with artificial urine with protein (RTAUP) are 33% (at 4MHz), 25% (at 5MHz), 20% (at 8MHz) and 15% (12MHz). However (MI)m values of the ribbons treated with healthy male urine (RTHMU) after 4h, 5h, 10h and 15h of incubation are 71% (at 3MHz), 57% (at 3MHz), 25% (at 6MHz) and 25% (at 5MHz), respectively. The saturation magnetization (Ms) values of RTAU after 3h, 6h, 12h and 24h of incubation are 71emu/g, 65emu/g, 63emu/g and 60emu/g respectively whereas, the respective Ms values of RTAUP are 73emu/g, 69emu/g, 67emu/g and 64emu/g. The Ms values of RTHMU after 4h, 5h, 10h and 15h of incubation are 96emu/g, 90emu/g, 75emu/g and 75emu/g respectively. The decrease in Ms and (MI)m values in RTAU and RTAUP compared to as-quenched ribbon is related to the amounts of various elements etched out from the ribbons and increased surface roughness. The Ms and (MI)m values of RTHMU are seen to have increased after 4h and 5h of incubation, due to strain relaxation through removal of strain developed during rapid quenching of the ribbons. On the other hand, the Ms and (MI)m values of RTHMU after 10h and 15h have decreased due to deterioration of the surface of the ribbons and thus, increase in magnetic (surface) anisotropy. The decrease in (MI)m and MS of RTAU with the time of incubation are more rapid compared to that of RTAUP, probably due to the larger surface anisotropy due to rapid deterioration of the surface of the RTAU than in RTAUP. Asymmetry in MI profiles of RTAU, RTAUP and RTHMU was observed and is attributed to the non-uniform etching of the surface of the ribbons leading to pinning of the domain wall motion.