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Abstract: Magneto-impedance (MI) of a double-barrier MgO magnetic tunnel junction (DMTJ) is measured as a function of frequency (20 Hz–3 MHz) and DC bias (−1 to 1 V) under magnetic parallel and antiparallel states. A strong nonlinear effect is observed at all frequencies and the MI changes from positive to negative at the relaxation frequency ∼1/RC. A frequency–dc bias () “phase diagram” is mapped out to describe the combination effects of the magneto-impedance response. The decay of the tunnel magneto-resistance (TMR) and tunnel magneto-capacitance (TMC) at high voltage is sufficiently reduced by the double-MgO barrier. The V1 / 2 (the voltage that magnetic response drops to 1/2 of its maximum) of TMC reaches an average value of ∼1.35 V, which is larger than the V1 / 2 of TMR ∼0.95 V, suggesting that the response of TMC is more stable than TMR for high frequency application. [ABSTRACT FROM AUTHOR]

We report on the preparation and characterization of the variation of B′-site transition metal in Sr2CrMO6 (M=Mo, W) with double perovskites structure. The magnetic susceptibility shows that Sr2CrMoO6 and Sr2CrWO6 are antiferromagnets with TN=40 and 30 K at H=1 T, respectively. In addition, a large magnetoresistance ratio (MR) of ∼38% (H=3 T) at 5 K was observed in the Sr2CrWO6 compound. However, the Sr2CrMoO6 compound does not show any significant MR even at high fields (MR∼4%; H=3 T and 5 K). The measured O K-edge X-ray absorption is in agreement with the calculated O p-density of states for both compounds. [Copyright &y& Elsevier]

Single-phase La1.2(Sr1.4Ca0.4)Mn2O7 has been synthesized from the aqueous solution of metal nitrates and citric acid by the sol–gel technique. Small particle size with high homogeneity of the powder was obtained. The valence of Mn is determined to be 3.45±0.05 by chemical titration. The MR ratio [ρ−ρ(H)]/ρ(H), is 115% (102 K, 1.5 T) for the composition prepared by the citrate route, and is nearly three times larger than that of the sample prepared by solid state reaction. [ABSTRACT FROM AUTHOR]

Abstract: The size dependence of magnetization reversal of magnetic tunnel junction (MTJ) rings has been investigated. The MTJ rings, with outer diameter of 4, 2 and 1μm and inner diameter of 1.5, 1 and 0.5μm were fabricated by a top–down technique. The magnetoresistance curves manifest all of the magnetic domain configurations during magnetization reversal in different sized rings. Various transition processes were observed, such as four transition, three transition and two transition in the largest, middle and smallest MTJ ring, respectively. Furthermore, the biasing fields observed from major loops decrease with decreasing size, which may result from edge roughness produced in the ion-milling process. [Copyright &y& Elsevier]