Investigation of Magnetic Properties of Cryogenically Cooled Electrolyte Iron-Silicon (Fe-Si) Powder

High permeable material is very important for the design of Micro Electro Mechanical Sensors (MEMS), where magnetic flux is used for the measurement. The present article deals with the investigation of the magnetic properties of the electrolyte iron-silicon powder as well as the sintered specimen developed from the same. A customized arrangement is used for the cryogenic cooling of the iron-silicon powder after annealing in the hydrogen environment. A powder with particle size 120 microns is initially heated at $550^{\circ} \mathrm{C}$ in a tubular furnace in hydrogen environment for one hour. Then it is cooled cryogenically in a vessel jacketed with liquid nitrogen. Magnetic characterization is performed for $\mathrm{Fe}-\mathrm{Si}$ powder and compacted specimens mad from the powder. To observe initial magnetization curve and B-H loop characteristics, a test set up is developed which uses an electromagnet placed around the specimen. This set up is capable of supplying variable DC current in the electromagnetic coil and measure magnetic flux density at one end of the specimen. The maximum magnetic permeability, remanence, and coercivity of the iron-silicon powder as well as the sintered specimen is determined experimentally. It is observed that cryogenic cooling results in improvement of $30 \%$ in maximum permeability without affecting the remanent magnetic flux.