A New Magnetic Material of High Permeability

This paper describes the preparation, heat treatment, and properties of supermalloy, a magnetic alloy of iron, nickel, and molybdenum. In the form of 0.014 in. sheet it has an initial permeability of 50,000 to 150,000, a maximum permeability of 600,000 to 1,200,000, coercive force of 0.002 to 0.005 oersted, and a hysteresis loss of less than 5 ergs/cm3/cycle at B=5000. Transformer cores made of insulated 0.001 in. tape, spirally wound, have about the same initial permeability and a maximum permeability of 200,000 to 400,000. The alloy has a Curie point of 400°C and appears to have an order-disorder transformation temperature somewhat above 500°C.