Thin Films of Heusler Alloy-Ni2(MnCu)(GaAl): Magnetic and Magnetocaloric Properties, Evidence of Vogel-Fulcher Relaxation

This study investigates the structural, magnetic, and magnetocaloric properties of thin films of a Heusler alloy with a composition of Ni2Mn0,7Cu0,3Ga0,8Al0,2. The films were produced by sputter deposition with thicknesses ranging from 32 to 300 nm on a Si (100) substrate with a 30 nm Ta adhesion layer. The structural transition at 260 K was observed only for the 300 nm thick film. All samples exhibit Curie temperatures around 300 K, which was also confirmed by electrical transport measurements. Hysteresis and magnetoresistance measurements revealed both antiferromagnetic and ferromagnetic behavior. This behavior was associated with spin glass and corroborated by fitting the data to the phenomenological Vogel-Fulcher (VF) model. The maximum magnetic entropy change observed was −4.8 J/kg
$\cdot $
K at 310 K when the magnetic field changed from 0 to 50 kOe.