Magnetostructural Phase Transition in Micro- and Nanosize Ni–Mn–Ga–Cu Alloys

The characteristic temperatures of the magnetostructural phase transition in lamella of the Heusler alloy Ni
₅₀
Mn
_18.5
Ga
₂₅
Cu
_6.5
increase with decreasing geometric dimensions to nanometers. The martensite phase was detected in the nanoscale portion at temperatures above M
_s
= 309 K by transmission electron microscopy, whereas only the austenite phase existed in the microsize part of the sample. The shift of the characteristic temperatures with decreasing sizes of samples must be taken into account when creating microelectromechanical systems based on Heusler alloys.