Coil-less fluxgate effect in CoNiFe/Cu wire electrodeposited under torsion

Co₁₉Ni_49.6Fe_31.4 layer was electrodeposited onto a twisted Cu wire and helical anisotropy was induced in the magnetic Co₁₉Ni_49.6Fe_31.4 shell. The magnetic and coil-less fluxgate (CF) properties are presented. The Co₁₉Ni_49.6Fe_31.4/Cu wire, produced at zero torsional strain, shows a CF output of nearly zero. The samples produced under torsional strains of 29.5π and 59π rad/m show a linear change in CF output in the low-frequency range. At higher frequencies the CF output shows two linear ranges. A maximum sensitivity of 150V/T is observed at 20 kHz driving-current frequency and 67 mA driving current for a wire produced under 59π rad/m torsional strain. It is also found that the slope of the CF curve depends on the direction of induced anisotropy.