High resistivity nickel-iron alloys with rectangular hysteresis loops

Because of its rectangular hysteresis loop, magnetically annealed 65/35 nickel-iron alloy is suitable for many applications. The alloy has a low resistivity, however, and eddy-current effects limit the performance of many devices made from the alloy. An alloy with similar magnetic characteristics and a higher resistivity is very desirable. A method of magnetic annealing is described which allows magnetic properties, practically identical to those of 65/35 alloy, to be induced in alloys containing up to 3% molydbenum, and nickel and iron in the ratio 65/35. The resistivity of the 3% molydbenum alloy is 53 μΩ cm, compared with 19 μΩ cm, for the binary 65/35 alloy. The new annealing method takes rather longer than that previously used, but is no more difficult to carry out; it can be used on alloys which cannot be successfully treated by a "normal" magnetic anneal. Compared with available 50/50 grain-oriented alloy, the 3% molybdenum alloy has a lower coercivity and a higher resistivity, but its saturation flux density is some 20% less.