Protective effect of a diamond-like carbon film on cobalt-based magnetoimpedance sensors in the Presence of Moisturized air

Abstract

High sensitivity of the magnetoimpedance (MI) sensors, and their dependence on the variation of the surface of the sensors, have limited their application in different environmental conditions, such as, moisturized air. Here, we studied the effect of moisture on a cobalt-based sensor in the MI ratio measurement. Scanning electron microscopy (SEM) images showed that the surface of the sensor after exposure to the moisture became rough. The effects of diamond-like carbon (DLC) film coated on a cobalt-based MI sensor were investigated with the aim of creating a stable MI sensor capable of working in various environmental conditions. No significant change was observed in the maximum MI ratio in different frequencies of the coated sensors after exposure to the moisture. SEM images showed that the surface of the DLC-coated cobalt-based ribbons (CBRs) remained almost unchanged after exposure to moisture. Measuring vibrating sample magnetometer showed that the variation in hysteresis loop in the coated sample after exposure to moisture is little. The appropriate stability of the DLC-coated CBRs in moisturized air can be useful for the development of amorphous ribbon-based MI sensors.