Ultra-thin Fe Films (4 (?)) Polarized Neutron Reflection

Ultrathin film 200A V/4A Fe/900A V/MgO(100) was prepared by Molecular Beam Epitaxy (MBE )method. The structure information of the thin film such as film thickness, surface and interface roughness was investigated by using both X-ray reflectometry (XRR) and polarized neutron reflectometry (PNR). The magnetization of the sample was studied by PNR measurement at different temperatures. By doing this work I have known the method of growing thin film (MBE), learnt the PNR method and also been familiar with the method and software for reflectivity data analysis. The experience that I have gotten in this work will be helpful for my further work on the new PNR instrument at CARR in CIAE.The sample was prepared using MBE method under ultrahigh vacuum (10^-10mbar). In the growing process a calibrated quartz crystal thickness monitor was used to control the thickness of each layer. And the clearness of each layer was detected by Auger electron spectroscopy (AES) in-situ measurement. Finally the X-ray rocking curve measurement demonstrated the good crystal quality of the thin film.XRR and PNR are complementary in studying the thin film. Both of them are sensitive to the film structure while PNR is also sensitive to the magnetization of thin films. The film thickness, interface roughness and information of oxide on the surface were gotten by doing both XRR and PNR measurement. The PNR experiment was carried out at temperatures from 10K to 295K in order to find out how the magnetization changes with temperature. The result demonstrates that the ultrathin Fe film has a ferromagnetic order. And the mean in-plane magnetic moment per atom is smaller than the bulk value. By fitting the magnetic moment per Fe atom dependence of temperature using power law the Curie temperature is deduced to be 310±30K.