Dynamic state switching in nonlinear multiferroic cantilevers Appl. Phys. Lett. 101, 043506 (2012) Nanomagnetism of cobalt ferrite-based spin filters probed by spin-polarized tunneling Appl. Phys. Lett. 101, 042409 (2012) Magnetic Schottky diode exploiting spin polarized transport in Co/p-Si heterostructure Appl. Phys. Lett. 100, 262402 (2012) Concepts and steps for the realization of a new domain wall based giant magnetoresistance nanowire device: From the available 24 multiturn counter to a 212 turn counter Exchange biased magnetic tunnel junction ͑MTJ͒ structures are shown to have useful properties for forming magnetic memory storage elements in a novel cross-point architecture. MTJ elements have been developed which exhibit very large magnetoresistive ͑MR͒ values exceeding 40% at room temperature, with specific resistance values ranging down to as little as ϳ60 ⍀͑m͒ 2 , and with MR values enhanced by moderate thermal treatments. Large MR values are observed in magnetic elements with areas as small as 0.17 ͑m͒ 2 . The magnetic field dependent current-voltage characteristics of an MTJ element integrated with a silicon diode are analyzed to extract the MR properties of the MTJ element itself.

We have used a self-aligned lithographic process to fabricate magnetic tunnel junctions of La 0.67 Sr 0.33 MnO 3 down to a few micrometers in size. We have obtained a magnetoresistance ratio as large as 83% at low magnetic fields of a few tens of Oe, which correspond to the coercivities of the magnetic layers. Transmission-electron-microscopy analysis has revealed the heteroepitaxial growth of the trilayer junction structure, La 0.67 Sr 0.33 MnO 3 /SrTiO 3 /La 0.67 Sr 0.33 MnO 3 . We have observed current-voltage characteristics typical of electron tunneling across an insulating barrier. The large magnetoresistance is likely due to the nearly half-metallic electronic structure of the manganites.

We have used a simple self-aligned process to fabricate magnetic tunnel junctions down to submicron sizes. Optical and electron-beam lithographies were used to cover a range of areas spanning five orders of magnitude. The bottom magnetic electrodes (Co or permalloy) in our junctions were exchange biased by an antiferromagnetic layer (MnFe). The top electrodes were made of soft magnetic materials (Co or permalloy). We have consistently obtained large magnetoresistance ratios (15%–22%) at room temperature and in fields of a few tens of Oe. The shape of the field response of the magnetoresistance was varied from smooth to highly hysteretic by adjusting the shape anisotropy of one junction electrode.

We report on the fabrication of a new class of trilayer epitaxial thin film devices based on the doped perovskite manganates La–Ca–Mn–O and La–Sr–Mn–O. We show that large resistance changes, up to a factor of 2, can be induced by a moderate applied magnetic field below 200 Oe in these trilayers supporting current-perpendicular-to-plane transport. These results show that low-field spin-dependent transport in manganates can be accomplished, the magnitude of which is suitable for magnetoresistive field sensors.

Industrial-use catalysts usually encounter severe deactivation after long-term operation for catalytic oxidation of chlorinate volatile organic compounds (CVOCs), which becomes a "bottleneck" for large-scale application of catalytic combustion technology. In this work, typical acidic solid-supported catalysts of MnCeO/HZSM-5 were investigated for the catalytic oxidation of chlorobenzene (CB). The activation energy (E), Brønsted and Lewis acidities, CB adsorption and activation behaviors, long-term stabilities, and surficial accumulation compounds (after aging) were studied using a range of analytical techniques, including XPS, H-TPR, pyridine-IR, DRIFT, and O-TP-Ms. Experimental results revealed that the Brønsted/Lewis (B/L) ratio of MnCeO/HZSM-5 catalysts could be adjusted by ion exchange of H• (in HZSM-5) with Mn (where the exchange with Ce did not distinctly affect the acidity); the long-term aged catalysts could accumulate ca. 14 organic compounds at surface, including highly toxic tetrachloromethane, trichloroethylene, tetrachloroethylene, o-dichlorobenzene, etc.; high humid operational environment could ensure a stable performance for MnCeO/HZSM-5 catalysts; this was due to the effective removal of Cl• and coke accumulations by HO washing, and the distinct increase of Lewis acidity by the interaction of HO with HZSM-5. This work gives an in-depth view into the CB oxidation over acidic solid-supported catalysts and could provide practical guidelines for the rational design of reliable catalysts for industrial applications.

We have measured the rate of thermally assisted magnetization reversal of submicron-sized magnetic thin films. For fields H just less than the zero-temperature switching field H(C), the probability of reversal, P(exp)(s)(t), increases for short times t, achieves a maximum value, and then decreases exponentially. Micromagnetic simulations exhibit the same behavior and show that the reversal proceeds through the annihilation of two domain walls that move from opposite sides of the sample. The behavior of P(exp)(s)(t) can be understood through a simple "energy-ladder" model of thermal activation.

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We present measurements of the magnitude of Néel “orange-peel” coupling due to interface roughness in a series of magnetic tunneling junction devices. Results from magnetometry and transport measurements are shown to be in good agreement with the theoretical model of Néel. In addition, we have used transmission electron microscopy to directly probe the sample interface roughness and obtain results consistent with the values obtained by magnetometry and transport methods.