Manganese-based compound films: MBE growth and magnetic properties

Abstract

Mn–based compounds are good candidate for many applications such as spintronics, magnetocaloric or hard magnet fields due to their unique electrical and magnetic properties. In this thesis, we used molecular beam epitaxy (MBE) for growing difference Mn-based compound thin films. In the first part, the structural and magnetic properties of FeMn2O4 films on MgO (001) were reported. The films show insulating behavior. In additional, the films present ferrimagnetic ordering with the Curie temperature (TC) above room temperature. In the second part, the epitaxial [MnAs(20Å)/GaAs(tGaAs)]4, tGaAs = 100, 200 and 300Å multilayer were grown on GaAs(001) substrate. The results addressed a possibility to control magnetic structure of the MnAs/GaAs hybrid quantum dot structure by changing thickness of GaAs layers. The magnitude of magnetization decreases from 163 to 48 emu/cm3 while the coercive field (HC ) increased from 494 to 690 Oe with GaAs thickness, respectively, due to increasing size of quantum dot. Finally, MnAs films were epitaxially grown on Al2O3 (0001) substrates. The epitaxial MnAs films were stable under tensile strain on Al2O3 (0001). The magnetocaloric effect (MCE) was found with maximum magnetic entropy change, ~ 35 J/kgK around magnetic phase transition by applying external magnetic field at 5 T. Our results addressed a possibility to use Mn-based compound thin films for spintronics, magnetocaloric fields.