Search

We have investigated the microwave oscillations due to a spin transfer effect induced by direct current in ferromagnetic nanocontact magnetoresistive (NCMR) elements with a current-perpendicular-to-plane spin-valve structure consisting of an FeCo/FeCo–AlOx nano-oxide layer/FeCo multilayer for the reference/spacer/free layers, respectively. Characteristic microwave oscillations were observed in the NCMR elements at different magnetization states induced by the application of a spin-polarized current, which are considered to be related to the introduction of a ferromagnetic NC to spacer layer (large interlayer coupling) and the resonance concerning the stability of the magnetization states of the free and reference layers around the NCs. A marvelously narrow full width at half maximum (FWHM) of l0–20 MHz is observed under a high applied magnetic field where the reference layer magnetization is slightly off axis relative to the pinned direction. By contrast, a wider FWHM of 80–600 MHz is observed at the magnetization state where the magnetization of the free layer just aligned to the antiparallel configuration against the magnetization of the reference layer. These characteristic results are discussed in terms of a spin dynamics mechanism induced by spin transfer torque in the free and reference layers around NCs. [ABSTRACT FROM AUTHOR]

An epitaxial wurtzite (WZ) Mg0.23Zn0.77O barrier based magnetic tunnel junction (MTJ), with electrode-barrier structure of Co0.30Pt0.70 (111)/Mg0.23Zn0.77O (0001)/Co (0001), was fabricated. The good crystallinity and tunneling properties were experimentally confirmed. Electrical and magnetic investigations demonstrated its high resistance-area product of 1.05MXlm2, a maximum tunneling magneto-resistance (TMR) of 35.5%, and the existence of localized states within the tunneling barrier producing TMR rapid decrease and oscillation when increasing the applied bias voltage. The TMR value almost vanished at 200 K, which was attributed to the induced moment and strong spin-orbit coupling in Pt atoms at the Co0.30Pt0.70/Mg0.23Zn0.77O interface. Owing to the ferroelectric behavior in WZ-MgZnO materials, the fabrication of WZ-MgZnO barrier based MTJs deposited on a metallic ferromagnetic electrode will open routes for electrically controllable non-volatile devices that are compatible with CMOS technology. [ABSTRACT FROM AUTHOR]

We clarify the origin of the interface perpendicular magnetic anisotropy (PMA) at the Cr2O3/ferromagnet interface by investigating the temperature dependence of the magnetic properties of Cr2O3/Co-Pt. We observed positive large interface PMA both above and below the blocking temperature of Cr2O3, with the PMA being less sensitive to temperature. Our results indicate that the effect of the metal/oxide interface, as well as that of the MgO/CoFeB interface, contributes strongly to the PMA at the Cr2O3/Co-Pt interface, although the effect of perpendicular exchange coupling might also slightly contribute to the interface PMA. [ABSTRACT FROM AUTHOR]

Deposition of ZnO thin films on a ferromagnetic metallic buffer layer (Co3Pt) by molecular beam epitaxy technique was investigated for realization of ZnO-based magnetic tunneling junctions with good quality hexagonal ZnO films as tunnel barriers. For substrate temperature of 600 °C, ZnO films exhibited low oxygen defects and high electrical resistivity of 130 Ω cm. This value exceeded that of hexagonal ZnO films grown by sputtering technique, which are used as tunnel barriers in ZnO-MTJs. Also, the effect of oxygen flow during deposition on epitaxial growth conditions and Co3Pt surface oxidation was discussed. [ABSTRACT FROM AUTHOR]