Enhancing the Squareness and Bi-Phase Magnetic Switching of CoFeSi Microwires for Sensing Application.

In the current study we have obtained CoFeSi glass-coated microwires with different geometrical aspect ratios, = d/D (diameter of metallic nucleus, d and total diameter, D). The structure and magnetic properties are investigated at a wide range of temperatures. XRD analysis illustrates a notable change in the microstructure by increasing the aspect ratio of CoFeSi-glass-coated microwires. The amorphous structure is detected for the sample with the lowest aspect ratio ( = 0.23), whereas a growth of crystalline structure is observed in the other samples (aspect ratio = 0.30 and 0.43). This change in the microstructure properties correlates with dramatic changing in magnetic properties. For the sample with the lowest -ratio, non-perfect square loops are obtained with low normalized remanent magnetization. A notable enhancement in the squareness and coercivity are obtained by increasing -ratio. Changing the internal stresses strongly affects the microstructure, resulting in a complex magnetic reversal process. The thermomagnetic curves show large irreversibility for the CoFeSi with low -ratio. Meanwhile, if we increase the -ratio, the sample shows perfect ferromagnetic behavior without irreversibility. The current result illustrates the ability to control the microstructure and magnetic properties of CoFeSi glass-coated microwires by changing only their geometric properties without performing any additional heat treatment. The modification of geometric parameters of CoFeSi glass-coated microwires allows to obtain microwires that exhibit an unusual magnetization behavior that offers opportunities to understand the phenomena of various types of magnetic domain structures, which is essentially helpful for designing sensing devices based on thermal magnetization switching.