Development of thin microwires with low Curie temperature for temperature sensors applications

A novel family of magnetic materials, thin ferromagnetic metallic glass-coated wires (1/30 μm in diameter) produced by the Taylor–Ulitovsky method present excellent magnetic properties such as magnetic bistability, GMI effect or enhanced magnetic softness attracting great attention for sensor applications. In this paper we report novel results on the fabrication and magnetic characterization of a number of Co–Fe–Ni–Si–B and Co–Fe–Cr–Si–B microwires with total diameter between 15 and 37 μm fabricated by the Taylor–Ulitovsky method with low Curie temperature possessing also good magnetic softness and high GMI effect. Magnetization, hysteresis loops, magnetic susceptibility and their magnetic field dependence and GMI effect at frequencies up to 500 MHz have been measured. Few samples possessing low TC (below 100 °C) also present high GMI effect with GMI ratio achieving 110% at 100 MHz. Additions of Ni or Cr to the conventional Co–Fe–Si–B composition with vanishing magnetostriction constant resulted in significant decreasing of the Curie temperature. Concrete applications have been designed such as the temperature sensors applications based on drastic change of the magnetic properties in the vicinity of Curie temperature.