Development of high quality ferromagnetic tunnel barrier and realization of tunneling spin filter devices

本文研究了具有垂直磁各向异性的铁磁绝缘体CoFe2O4的隧道自旋滤波效应。为了改善CoFe2O4薄膜的表面平整度，采用带荫罩的脉冲激光沉积法在MgO(001)衬底上生长CoFe2O4薄膜。得到了无液滴形成的CoFe2O4薄膜，其垂直各向异性能量密度为2.36×106erg/cm3。用制备在MgO(001)衬底上的MgO/CoFe2O4和铁磁性金属L10型FEPD电极测量了磁隧道结(MTJ)的磁阻。MTJ的隧道磁电阻率在5K时为0.7%，300K时为16.5%。

In this study, tunneling-spin filtering effect of ferromagnetic insulator CoFe_2O_4 with perpendicular magnetic anisotropy was studied. To improvement surface flatness of CoFe_2O_4 films, the films were grown on MgO(001) substrates by pulse laser deposition method with a shadow mask. The CoFe_2O_4 films without droplet formation with perpendicular anisotropy energy density of 2.36x106 erg/cm3 were obtained. Magnetoresistance measurements were carried out for magnetic tunnel junctions (MTJs) using MgO/CoFe_2O_4 and ferromagnetic metal L10-type FePd electrodes fabricated on MgO (001) substrates. The tunnel magnetoresistance ratio of 0.7% at 5 K and 16.5% at 300 K was obtained for the MTJs.