The magnetic properties and structure of Fe3O4 thin films under different preparation conditions have been evaluated. The main deposition parameter in this study was the ratio of water vapor partial pressure to argon partial pressure. TEM images showed that the surface structures are homogeneous for the different preparation conditions. STM study offered in more detail three-dimensional surface patterns. Temperature dependence of the coercivity and its relation to different Fe-oxide phases are reported. The relation of resistivity to the temperature provides further evidence that the Verwey temperature is a good criterion to distinguish the completion of Fe3O4 to gamma-Fe2O3 transformation. The results of magneto-optical Kerr effect measurements and magnetic measurements using a VSM are also compared.