Magnetoresistance at Room Temperature of Oleic Acid Coated Fe3-xCoxO4 (x = 0, 0.1 and 0.3) Nanocrystal Drop-Cast Films

Oleic acid coated Fe3-xCoxO4 (x = 0, 0.1 and 0.3) nanocrystal self-assembled films were fabricated via drop-casting of colloidal particles on a SiO2/Si substrate. Nanocrystals of the Fe3-xCoxO4 exhibited bifurcation of the zero-field-cooled and field-cooled magnetizations at 300 K. The Fe3-xCoxO4 nanocrystal drop-cast films demonstrated nonlinear current-voltage characteristics between the source and drain electrodes in magnetic fields of zero and 0.2 T, and magnetoresistance reached into −46% for the x = 0 film and −50% for both the x = 0.1 and 0.3 films at 300 K. Oleic acid coated Fe3-xCoxO4 (x = 0.1 and 0.3) nanocrystal would boost developments of a high performance current switching device using negative magnetoresistance

Composition and structure of Pd nanoclusters in SiOx_x thin film

The nucleation, distribution, composition and structure of Pd nanocrystals in SiO$_2$ multilayers containing Ge, Si, and Pd are studied using High Resolution Transmission Electron Microscopy (HRTEM) and X-ray Photoelectron Spectroscopy (XPS), before and after heat treatment. The Pd nanocrystals in the as deposited sample seem to be capped by a layer of PdO$_x$. A 1-2 eV shift in binding energy was found for the Pd-3d XPS peak, due to initial state Pd to O charge transfer in this layer. The heat treatment results in a decomposition of PdO and Pd into pure Pd nanocrystals and SiO$_2$

Magnetoresistance of Drop-Cast Film of Cobalt-Substituted Magnetite Nanocrystals

An oleic acid-coated Fe2.7Co0.3O4 nanocrystal (NC) self-assembled film was fabricated via drop casting of colloidal particles onto a three-terminal electrode/MgO substrate. The film exhibited a large coercivity (1620 Oe) and bifurcation of the zero-field-cooled and field-cooled magnetizations at 300 K. At 10 K, the film exhibited both a Coulomb blockade due to single electron charging as well as a magnetoresistance of ∼−80% due to spin-dependent electron tunneling. At 300 K, the film also showed a magnetoresistance of ∼−80% due to hopping of spin-polarized electrons. Enhanced magnetic coupling between adjacent NCs and the large coercivity resulted in a large spin-polarized current flow even at 300 K

Large frequency dependence of lowered maximum dielectric constant temperature of LiTaO3 nanocrystals dispersed in mesoporous silicate

A large frequency dependence of the maximum dielectric constant temperature was observed for LiTaO3 nanocrystals (the diameter 20 Å) dispersed in mesoporous silicate. At the applied field frequency of 100 kHz, the maximum temperatures in the real and imaginary parts were 365 and 345 °C, respectively. The maximum temperature in the real part is apparently lower than the paraelectric–ferroelectric transition temperature (645 °C) of bulk LiTaO3. The maximum temperature in the imaginary part rose from 285 to 420 °C with increasing frequency from 10 to 1000 kHz. Since the bulk LiTaO3 shows no relaxor behavior, such superparaelectric behavior is obviously a consequence of nanominiaturization of LiTaO3 crystal and insignificant cooperative interactions between the nanoparticles

Effects of hydrogen in working gas for sputter-deposition on surface morphology and microstructure of indium tin oxide thin films grown at room temperature

Surface morphology and microstructure of indium tin oxide (ITO) thin films sputter deposited without heat treatment were obviously different from each other depending on the hydrogen concentration [H] in the working gas. The film surface became smoother with increasing [H] to 1%, but nucleation and growth of grains were apparent above [H] = 1.5%. The width of columnar grains in the ≤200 nm-thick films narrowed from ≈100 nm to ≈50 nm with increasing [H] from 0% to 1.5%. Randomly oriented and agglomerated grains were observed for the film deposited with [H] = 3.6%. Hydrogen added to the working gas induced reduction of the grain size, and then resulted in lowering of the carrier mobility

Effects of (HoxIn1-x)1.9Sn0.1O3 matrix on magnetization of dispersed Fe3O4 nanocrystals

Solid solutions (HoxIn1−x)1.9Sn0.1O3 with x = 0–0.3 were synthesized to employ as dispersion matrix for oleic acid coated Fe3O4 nanocrystals (NCs). The x = 0.05 matrix exhibited a resistance minimum at a non-zero temperature in each temperature dependent resistivity with magnetic fields of 0 and 1 T, and a negative magnetoresistance. The sample of oleic acid coated Fe3O4 NCs dispersed in the x = 0.05 matrix showed enhanced spontaneous magnetization as the factor of ≈1.3 relative to as-synthesized oleic acid coated Fe3O4 NCs