Minor loop loss predictions in devices using permanent magnet materials

Experimental work is described which indicates the feasibility of making minor loop loss predictions in devices which use permanent magnet materials. The methods of making these loss predictions and some general conclusions about losses are discussed. Minor loop loss predictions are important in any device in which the material undergoes high-frequency operation along recoil or incremental permeability lines. However, little has been published about minor loops in permanent magnet materials. In Alnico 5, the hysteresis (zero frequency) component of the minor loop is found under certain conditions to exhibit a small secondary loop superimposed upon the major loop. The behavior of this secondary loop with variation of temperature gives insight into the behavior of one of the phases of the material and shows that improper metallurgical heat treatment can degrade the over-all permanent magnet characteristics.