On the crystal growth and magnetism of Fe on MgO and MgAl₂O₄

We report on the epitaxial growth of thin Fe layers on single-crystalline MgAl₂O₄ substrates. Compared to Fe thin films grown on single-crystalline MgO substrates, exhibiting strain induced by the 4% lattice mismatch, sputter-deposited Fe films on single-crystalline MgAl₂O₄ substrates have a lattice mismatch of around 0%. Their structural and magnetic properties are systematically analyzed for different deposition parameters and Fe layer thicknesses and compared to identically grown films on MgO substrates. The results of this study show that Fe thin films deposited on MgAl₂O₄ substrates exhibit improved crystal quality resulting in the observation of clear Laue oscillations around the Fe(002) peak as well as an approximately 40 times smaller FWHM of the rocking curve compared to Fe grown on MgO. Fits of the Laue oscillations suggest that over 91% of these 50 and 100 Å thick Fe layers scatter coherently. Investigations of the magnetic properties show smaller saturation fields for Fe deposited on MgAl₂O₄ resulting from the low stress in the Fe lattice. Such Fe films may potentially find application in devices which depend strongly on the overall crystal structure and/or interface quality.