Search

Recently, unusual magnetic properties were found experimentally in otherwise diamagnetic nanoparticles. Our experiments and analysis revealed that a universal expression can describe the size-dependent magnetic moments in ultrafine diamagnetic systems, including Au, Pd, and HfO2 nanoparticles. A model was presented to explain the observed phenomenon. It suggested that the up and down spins in ultrafine diamagnetic systems are spatially separated and form asymmetric spin-singlet pairs. The correlation lengths of the spin-singlet pairs in Au, Pd, and HfO2 nanoparticles were estimated to be about 1.65, 13, and 4.4 nm, respectively. On the basis of this model, we explain (a) the origin and the size dependence of magnetic moments in diamagnetic nanoparticles, and (b) the origin of the extremely large anisotropy in diamagnetic nanoparticles. [ABSTRACT FROM AUTHOR]

We have fabricated a heterojunction by depositing La0.67Ca0.33MnO3 film on electron doped silicon wafer with a buffer layer of natural SiO2. The current-voltage measurement shows that it is a diode with a good rectifying property in a wide temperature range. At high positive voltages, the current-voltage curve shows space charge limited (SCL) current behavior, manifesting itself as a SCL diode. At low positive and negative voltages, the resistance of the junction shows a peak at a certain temperature, which decreases with increasing positive voltage and keeps constant at negative voltages. Magnetoresistance of the junction shows a similar temperature dependence as the resistance of the junction. Calculations show that these phenomena can be attributed to the depletion layer of the La0.67Ca0.33MnO3 film. This work also demonstrates that SCL diode can be realized in La0.67Ca0.33MnO3/SiO2/Si with the presence of the SiO2 layer. [ABSTRACT FROM AUTHOR]

Research is done on the structure, magnetic and transport properties of the compounds Bi0.5Ca0.5Mn (sub 1-x) CrxO3 (BCMCO) with 0

Anatase thin films of pure TiO2 and 6% niobium doped TiO2 (Nb:TiO2) were fabricated on LaAlO3(100) by pulsed laser deposition. The electrical properties of Nb:TiO2 films are grain-size dependent, i.e., the larger grain size, the higher conductivity, and mobility. For all TiO2 and for Nb:TiO2 with small mean grain size (d<15 nm), the band gap energy is found to increase systematically with the decrease in d, which is consistent with the quantum confinement model. For the films with large mean grain size (d>15 nm), particularly, a blueshift in Nb:TiO2 is governed by the Burstein–Moss effect. [ABSTRACT FROM AUTHOR]

The capacitance characteristics of La0.5Ca0.5MnO3/Nb–SrTiO3 p-n junction and magnetic property have been investigated. The magnetic field-induced increase in ferromagnetic metallic phase, irreversibility, and the exchange bias effect were observed. The junction also shows a remarkable thermal hysteresis of capacitance, a giant positive magnetocapacitance (MC), a remarkable difference of MC for the zero field cooling and field cooling processes, and a memory effect of magnetic field. The results can be understood in terms of phase separation. This work demonstrates the remarkable tunability of the capacitance for phase separated manganite heterojunctions, which may have potential applications. [ABSTRACT FROM AUTHOR]

The authors report the current-voltage characteristics of La0.5Ca0.5MnO3/Nb-SrTiO3 p-n junction. This junction shows remarkable thermal hysteresis, giant negative magnetoresistance (MR), remarkable differences of MR for the zero field cooling and field cooling processes, and memory effect of magnetic field. Magnetic force microscopy studies provide direct evidence of magnetic inhomogeneity in La0.5Ca0.5MnO3 film. These intriguing behaviors of our p-n junction can be explained by the phase separation in La0.5Ca0.5MnO3. This work demonstrates the principle of harnessing phase separation for highly tunable device applications. [ABSTRACT FROM AUTHOR]

The authors have fabricated LiNbO3/La0.69Ca0.31MnO3 heterojunctions by growing LiNbO3 on La0.69Ca0.31MnO3 single crystals. Rectifying behavior was found in these junctions, which can be tuned by applied magnetic field. A band diagram is proposed to account for the junction behavior. A voltage pulse-induced resistive switching was also observed, which can be understood by considering the ferroelectric polarization at the junction interface. The ability to tune transport properties of ferroelectric-ferromagnetic heterojunctions by magnetic field and electric polarization is potentially significant for their electronic applications. [ABSTRACT FROM AUTHOR]

The authors report the current-voltage characteristics of CaMnO3-δ/La0.69Ca0.31MnO3 heterojunctions prepared under different oxygen pressures. The most interesting observation is that the heterojunctions made under low oxygen pressure shows an ultrasharp current jump in the current-voltage curves and the nonlinear coefficient can reach ∼2×104. They also show remarkable magnetoresistance. The results can be understood in terms of the oxygen vacancy related defects at the junction interface. This work shows that all-manganite-based heterojunctions can show giant nonlinear coefficient, which may have potential applications. [ABSTRACT FROM AUTHOR]

Fe3O4/SiO2/Si heterojunction was fabricated by growing Fe3O4 film on an n-typed Si wafer with the native SiO2 buffer layer using the pulsed laser deposition. Transmission electron microcopic study shows the high quality of the heterojunction interfaces and the SiO2 layer is 2.5 nm thick. This junction shows a backward diodelike rectifying behavior and an anomalously giant positive magnetoresistance (MR) for the large reverse bias voltages. The temperature dependence of MR shows a peak around the Verwey transition temperature with a maximum MR of 87% under a -2 V bias voltage. The results were discussed by considering the band structure of the heterojunction and the effect of the reverse bias voltage. [ABSTRACT FROM AUTHOR]