Spintronic materials, physics and device designs

Recently, in the State Key Laboratory of Magnetism amorphous Al-O barrier based magnetic-tunnel-junctions (MTJs) with ring-shaped structures and a tunneling magnetic resonance ratio of 80% at room temperature were micro-fabricated. High ordered FePt and antiferromagnetic (Cr25Mn25)Pt50 thin films with good thermal stability and high coercivity were also synthesized. Large current-induced resistance effects in colossal magnetic resonance thin films was observed. A new method was designed to observe spin flip scattering in the nanometer sized spacer layer near the ballistic limit based on MTJs. An important first-principles study of quantum well (QW) states and QW-resonance tunneling in the symmetric epitaxial Fe(001)/MgO/Fe/MgO/Fe double barrier MTJ was performed. Electron spin resonance spectra was successfully used to investigate the interlayer exchange coupling and anisotropic spin structures in layered transition metal oxides. An ultrahigh sensitivity Hall effect was observed in CoFe/Pt multilayers via manipulation of the perpendicular interface anisotropy due to the strong spin-orbit interaction of Pt. Nano-ring MTJs and 4×4 bit nano-ring magnetic random access memory (MRAM) demo devices were fabricated with spin-polarized current (spin transfer torque) switching, which may open a new way for developing MRAM devices.