Ferromagnetic thin films were combined with piezoelectric substrates with the purpose of obtaining voltage controllable magnetization behavior. The interface between the ferromagnetic and piezoelectric material was examined for optimized voltage controlled magnetic response. Magneto Optic Kerr Effect (MOKE) measurements, supported by atomic force microscopy (AFM), showed the need to polish the piezoelectric substrates to a roughness below 1nm RMS (1*1νm2scan) for a minimum coercivity of 3kA/m. The magnetic anisotropy dependence on deposition, and anneal temperature was determined, and was shown to cause temperature driven coercivity changes up to 45 A/Km. A buffer layer between the piezoelectric substrate and the ferromagnetic thin film doubled the relative importance of the voltage driven magnetic effects.