Fabrication of GeNi₂O₄, GeCu₂O₄, and MgCr₂O₄ Epitaxial Thin Films

In the AB₂O₄ spinel system with B site magnetic, a rich variety of magnetic and orbital frustration has been observed. Highlighted phenomenons like spin-liquid phase and field-induced novel phase transitions were seen in these single-crystal systems extensively. Here we report on the first growth of the (001)-oriented GeNi₂O₄, (001)-oriented GeCu₂O₄ and (111)-oriented MgCr₂O₄. All fabricated films were characterized by X-ray diffraction and X-ray photoelectron spectroscopies confirming both crystalline epitaxy and chemical stoichiometry. Synchrotron-based X-ray absorption spectroscopies were also carried out to prove the correct electronic state. The availability of single-crystalline thin films can pave the road to understand the magnetic ordering of differently-oriented spinels in an ultra-thin limit.