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Zhang J.,Ningbo Institute of Materials Technology and Engineering | Zhang J.,Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology | Zhang J.,Hebei University of Technology | Song J.-Z.,Hebei University of Technology | And 7 more authors.
IEEE Transactions on Magnetics | Year: 2011

The magnetization reversal mechanism and temperature dependence of magnetic properties of Cr(50 nm)/[SmCo6(9 nm)/Cu(x, nm)/Fe(5 nm)/Cu(x, nm)]6/Cr(100 nm)/a-SiO2,(x=0-0.75) exchange spring multilayer films are reported. The initial curves and angular-dependent coercivities measurement indicate that the magnetization reversal mechanism of multilayer films is determined by domain-wall pinning. With lowering the temperature, the coercivities of multilayer films increase largely. By inserting Cu layer between the hard and soft layers can increase the coercivity of the multilayer films, especially at low temperatures. The hysteresis loops of the film with x=0.75 annealed at 500 °C measured from 10 to 400 K show all the single-phase behavior, although the film contains a large amount of soft phase (≈ 40 vol%), indicating the strong exchange coupling between the hard and soft phase and the extremely large nucleation field in the soft layers. With the decrease of temperature, the maximum energy product (BH)max and remanence also increase. A large (BH)max of about 37.4 MGOe is obtained at 10 K for the film with x=0.75 annealed at 500 °C. The recoiling curves as well as the irreversible change in magnetization -Δ M irrev(H)/2Mr=[Mr-Md(H)]/2M r versus the reverse field H demonstrate the increase of the inhomogeneity and pinning in the hard layer at the low temperature as well as after the addition of Cu, therefore, an improved coercivity. © 2011 IEEE.


Zhuge F.,Ningbo Institute of Materials Technology and Engineering | Zhuge F.,Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology | Hu B.,Ningbo Institute of Materials Technology and Engineering | Hu B.,Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology | And 8 more authors.
Carbon | Year: 2011

The mechanism of the resistive switching (RS) effect in graphene oxide (GO) thin films prepared by the vacuum filtration method has been investigated by macroscopic current-voltage (I-V) measurements and conducting atomic force microscopy (CAFM). Detailed I-V measurements show that in metal/GO/Pt sandwiches, the RS originates from the formation and rupture of conducting filaments. An analysis of the temperature dependence of the ON-state resistance reveals that the filaments are composed of metal atoms due to the diffusion of the top electrodes under a bias voltage. Moreover, the RS is found to occur within confined regions of the metal filaments. The RS effect is also observed in GO/Pt structures by CAFM. It is attributed to the redox reactions between GO and adsorbed water induced by external voltage biases. © 2011 Elsevier Ltd. All rights reserved.

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