Investigation of Magnetic Proximity Effect in Ferromagnet/superconductor Thin Films by Low Temperature Magneto Optical Kerr Effect Measurement

Download or read book Investigation of Magnetic Proximity Effect in Ferromagnet/superconductor Thin Films by Low Temperature Magneto Optical Kerr Effect Measurement written by David A. Christiansen and published by . This book was released on 2012 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A room temperature Magneto Optical Kerr Effect (MOKE) experimental setup was expanded to improve performance and integrated with a liquid Helium cryogenic system. Ferromagnetic/superconductor hybrid systems have recently been intensively studied due to their interesting proximity effect and the possible applications such as a current switching device. Most of previous work focused on the superconducting property change due to the presence of the ferromagnet but not much research of the magnetic property change due to the superconducting transition has been done. Using the extended MOKE setup, magnetization from the top ferromagnetic layer can be measured below and above the critical temperature of the superconducting thin film layer. Temperatures as low as 4.2K were achieved and the magnetization with respect to applied magnetic field of a Permalloy/Niobium (Py/Nb) thin film was measured at 295K, 11K, and 4.2K. Coercivity increased as temperature decreased. A magnetization measurement with constant applied magnetic field was also performed with a temperature sweep passing the superconducting transition. However, due to temperature instability it was difficult to compare the magnetization above and below Tc of the Nb. Both hysteresis loops above and below the superconducting critical temperature were measured to be similar within the measurement error and have a coercivity of 160 ±16 Oe. Reasons for not detecting a magnetization change due to the superconductor could be either due to sample heating, thermometer calibration, the limited accuracy of measuring the coercivity in this sample, or the change due to the SC may be smaller or not exist.