Initiation of flux reversal in magnetic-amplifier cores

Flux reversal in grain-oriented nickel-iron tape cores has been described by several models during recent years.1,2 Some difference of opinion, however, still exists with regard to the initiation of the process.1 New evidence is here set forth that nucleation and initial growth of regions or domains of reverse magnetization occur near the tape surface for applied fields sufficiently larger than the coercive force Hc of the material. Fields at least twice the coercive force will be considered. More evidence is still needed to substantiate models for fields only slightly in excess of Hc. Initial growth will be discussed, both for cores previously saturated and for those not saturated when flux reversal was initiated. The latter case, though of particular interest in many applications of ¿square-loop¿ magnetic cores, has not been treated adequately so far.