Study On Large Enhanced Perpendicular Magnetic Anisotropy In Co₉₀Fe₁₀/Pd Thin Films

Magnetic multilayers exhibiting perpendicular magnetic anisotropy (PMA) have a extremely high value of research in perpendicular magnetic recording media as well as in perpendicular spin valves and magnetic tunnel junctions. The Pd/Co based multilayers with PMA is one of the key issues in recent years. In this dissertation, the Fe doped Co/Native Oxide/Pd thin films have been prepared with their perpendicular magnetic anisotropy systemically investigated, the details are as follow:A bottom electrode structure of spin valves (SVs) is investigated, the film stacks Pd(3nm)/CoFe(0.8nm)/native oxide/CoFe(t nm)/Cu(4nm)/Pd(5nm). The results indicate that the magnetic anisotropy of the film has been transformed from in-plane to out-of-plane after annealing, and the strong perpendicular magnetic anisotropy (PMA) is still presented even for the film with effective CoFe thickness as large as2nm. This kind of bottom electrode film with non-multilayer structure, thick ferromagnetic layer and high thermal stability is beneficial to the development of the spin transfer torque all-metal pseudo-spin-valves with perpendicular anisotropy.A series of CoFe/Pd bilayer thin films by introducing a native oxide layer to the interface or to the inside of CoFe layer have been fabricated and investigated. The researches indicate that the magnetic anisotropy of the films has been transformed from in-plane to out-of-plane after annealing by introducing the native oxide layer. As to the samples with the introduction of native oxide layer into CoFe layer, the strong perpendicular magnetic anisotropy is maintained in a wide range of the effective thickness (1.2～2nm) of magnetic layer. As the perpendicular magnetic films, the thickness of CoFe layer in this special bilayer structure is at least1.4nm thicker than in common CoFe/Pd multilayer structure. The researches in this paper are beneficial to the fabrication of the electrodes in perpendicular magnetic devices with high thermal stability.Perpendicular magnetic anisotropy (PMA) in Co-rich Co90Fe10/native oxide/Pd films is investigated。After300℃annealing, the magnetic anisotropy of the films transformed from in-plane to out-of-plane for samples with CoFe layer thickness more than1.8nm. In addition, the annealed Pd/CoFe/MgO films exhibits better perpendicular magnetic anisotropy than annealed Pd/CoFe/Cu films. The interface of native oxided CoFe/MgO is believed to cause the additional PMA observed. Moreover, magnetic tunnel junctions multilayers with thick perpendicular ferromagnetic electrodes using these structures have been fabricated and studied.