Effect of the AIN buffer layer on the characteristics of the GaAs/ (MnZn)Fe2O4 structures has been investigated with atomic force microscopy, high resolution X-ray diffraction (HRXRD), and reflection high-energy electron diffraction (RHEED). We have found that the use of the AIN buffer layer improves crystalline quality of GaAs thin films. HRXRD and RHEED observations have revealed that the epitaxial relationship for this structure is GaAs(1 1 1)//AlN[0 0 0 1]//(MnZn)Fe2O4 [1 1 1 ] and GaAs [1 - 10]//AlN[1 0 - 1 0]//(MnZn)Fe2O4[1 - 10]. We have also found that the surface morphology is remarkably improved by the use of AlN buffer layer. (C) 2003 Elsevier Science B.V. All rights reserved.