Magnetic analysis of MnAs films grown on GaAs and Si substrates for potential spintronics and magnetocaloric applications

摘要

We present a magnetic characterisation of MnAs films grown by MOVPE on semiconductor substrates for comparing the effect of thickness and substrate on their magnetic and magneto-thermal properties with particular focus on the nature of the magneto-structural transition between the ferromagnetic hexagonal α-phase and the paramagnetic orthorhombic β-phase. The nature of this transformation depends on the presence of strain and turns out to be of second-order type for epitaxial-crystalline MnAs/(0 01)GaAs films and closer to a first-order type for polycrystalline MnAs/SiO_2/Si films. The magnetocaloric effect at the transition has been estimated for thin film samples, resulting appreciably lower than that of bulk MnAs.