Study of Magnetizing Processes in ${\hbox{Ni}}_{50}{\hbox{Mn}}_{35}{\hbox{In}}_{15}$ Heusler Alloy

In the vicinity of the first-order transition temperature, the Ni
₅₀
Mn
₃₅
In
₁₅
Heusler alloy exhibits interesting magnetizing processes. The virgin curve at 280 K lies entirely outside the major loop, and the area of the MH loop formed by the virgin curve and the sequential descending curve is significantly larger than that of the major loop. At 275 K, the virgin curve lies slightly outside the major loop, and the area of the loop containing the virgin curve is slightly larger than that of the major loop. These differences are attributed to the different initial magnetic states of the alloy at the two temperatures. The initial state at 280 K is a mixed state, consisting of a low magnetization majority phase and a high magnetization minority phase. The initial state at 275 K is almost all the low magnetization phase. At both temperatures, a strong enough field converts the low magnetization phase to the high magnetization phase. The initial state affects the reverse transition from high to low magnetization phase upon cycling the field back to zero. The behavior of the virgin curve, major loop, and related properties is a complex function of the field and initial state. Similar behavior is expected in other Heusler alloys and other materials exhibiting first-order magneto structural transitions.