Magnetic Characterization of Soft Magnetic Cores at Cryogenic Temperatures

It is important to investigate and understand the magnetic properties of soft magnetic materials at cryogenic temperatures for the optimal design of superconducting machines and superconducting transformers. The magnetic properties of soft magnetic materials at room temperatures have been studied extensively. However, there is almost no information available for the magnetic properties of these materials at cryogenic temperatures. This paper for the first time presents the experimental results for the magnetic characterization of four soft magnetic materials from room temperature down to 21 K. The experimental results demonstrate that the core losses at 21 K is higher than room temperature for all the materials. They also show that the permeability of all the materials reduce at 21 K compared to room temperature. The optimal temperature in terms of the best magnetic properties is identified for each material. The data presented in this paper will provide valuable guidance for practical design and optimization of superconducting machines and superconducting transformers with soft magnetic cores.