Stress-induced anisotropy in LPE grown Ni(Fe,Al)2O4 films

Preliminary results are reported about the growth of single crystal Ni(Fe,Al)₂O₄ films, grown by means of liquid phase epitaxy on (111)MgO and on (111)ZnGa₂O₄ substrates using a PbO-B₂O₃-Fe₂O₃ solvent. While films grown upon MgO show stress relief at the growth temperature, films grown upon ZnGa₂O₄ possess a tensile strain due to elastic deformation. Since λ₁₁₁ for NiFe₂O₄ is strongly negative a stress-induced uniaxial anisotropy is present in the films. Stripe domains can be observed with the Bitter technique and when a magnetic field is applied perpendicular to the plane of the film, magnetic bubbles with a diameter of ～2 μm appear. A bubble stability factor q exceeding unity is obtained. For the first time magnetic bubbles are found in LPE grown spinel ferrites.