Effects of Surface Polarity on the Structure and Magnetic Properties of Epitaxial h-YMnO₃Thin Films Grown on MgO Substrates

YMnO₃(YMO) thin film is one of the highly studied multiferroic materials due to its tunable crystalline structure via misfit strain from the substrate. This tunability involves intriguing physical phenomena that encourage further explorations for fundamental research and practical applications. The configuration of the initial atomic layers during the growth of YMO thin films plays a key role in determining their physical properties. In the present research, the correlation between the substrate's polarity and the misfit strain of the YMO films is studied comprehensively. The results showed that despite the YMO films grown on MgO (100) and MgO (111) being under the same growth conditions and having resulted in the same hexagonal crystal structure (h-YMO), the films do exhibit distinctly different microstructures, electronic structures, and magnetic properties. We suggest that the extent of charge accumulation induced by the surface polarity of the substrates may have resulted in a substantially different intermixing feature at the h-YMO/substrate interfaces, which, in turn, alters the structure and thus the physical properties of the films. Our results open up the possibility of manipulating the h-YMO thin film's magnetic properties by interfacial engineering without significantly altering the structure of the films which could benefit the fabrication efficiency for various next-generation electronics.