Materials Literature
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A detailed study of the magnetization M(H,T) of manganites near TC is presented. Analysis, in the framework of Landau theory of phase transitions (G=G0+1/2AM2+1/4BM4+1/6CM6−MH) reveals that for La0.67Ca0.33MnO3 (TC=267 K), La0.8MnO3 (TC=250 K), and La0.60Y0.07Ca0.33MnO3 (TC=150 K) the phase transition is first-order a…
Magnetic anisotropy of sputtered epitaxial La2/3Ca1/3MnO3 (LCMO) thin films grown on top of LaAlO3 (LAO) substrates has been studied as a function of thickness. A series of films with thickness ranging from 20 to 150 nm have been prepared. LCMO films grown on LAO substrates are subjected to an in-plane biaxial compres…
We discuss the condition for delocalization of holes in N-doped ZnO, ZnS, and ZnTe. For N-doped ZnO and ZnS, we find large energy reduction due to ionic polarization and a narrow N-impurity band at the top of the valence band compared with those for N-doped ZnTe. These are due to the significant difference between the…
Formation of Ce3Fe29−x−yCoxMoy(x=0,3,6,10) compounds has been investigated by means of x-ray diffraction and magnetic measurements. It is found that the required Mo content to stabilize the 3:29 compounds decreases monotonically as Co content increases, totally different from the discovery in the Gd3(Fe1−xCox)29−yCry…
Gold nanoclusters dispersed in single crystal MgO have been prepared by ion implantation at 975 K and subsequent annealing at 1275 K for 10 h. The morphological features, size, and crystallographic orientation of the Au nanoclusters with respect to the MgO matrix, as well as the interface structure between the Au nano…
Magnetic and magnetostrictive properties of amorphous Tb-Fe thin films are investigated as functions of sputtering conditions such as the substrate thickness, input power, sputtering time, and coverage area ratio of coated thin film to substrate. The observed magnetic and magnetostrictive properties are well explained…
We have fabricated and characterized epitaxial Fe3O4/CoCr2O4/La0.7Sr0.3MnO3 magnetic trilayer junctions (MTJs) grown on (110) and (100) SrTiO3 substrates. Large inverse junction magnetoresistance (JMR) as high as −25% has been observed at a field of 4 kOe in (110) oriented MTJs. The improvement of the JMR over that ob…
The effect of applying a magnetic field during the crystallization process of a melt-spun Nd2.4Pr5.6Dy1Fe85B6 alloy on the nanostructure, crystallographic texture, exchange coupling, and magnetic properties has been studied. Compared with samples annealed without magnetic field, there was a noticeable improvement in t…
An experimental study of the magnetic properties of the Pr0.5Ca0.5Mn0.97Ga0.03O3 perovskite manganite is presented. The ac magnetic susceptibility measurements show that the low T orbitally and charge ordered state has been destabilized by the nonmagnetic impurity substituted for Mn. In this compound, at 2.5 K, well-d…
The Er–Tm interaction and its effect on the luminescence from Er–Tm codoped silicon-rich silicon oxide (SRSO) is investigated. Er and Tm ions were implanted into SRSO films, which consist of Si nanocrystals embedded in a SiO2 matrix. A broad luminescence spectrum extending from 1.5 to 2.0 μm was observed under excitat…
The growth mode of ZnO on a-plane (11 0) sapphire in metal-organic vapor phase epitaxy exhibited stronger tendency toward three-dimensional nucleation at lower temperature (≤700°C) and toward two-dimensional layered growth at higher temperature (900°C), resulting in the formation of rods and films, respectively. ZnO n…
Photoconductivity (PC), thermally stimulated conductivity (TSC), photoluminescence (PL), thermoluminescence (TL), and electron spin resonance (ESR) measurements have been made on single crystals of potassium tantalate over the temperature range 4.2–290 K. We revealed two sorts of O− shallow hole centers which are resp…
It is known that the substitution of Co for Fe gives rise to increases in magnetization and Curie temperature, not only in the bcc metals, but also in intermetallic compounds and alloys as well. With the expectation that this is the case in Co-substituted FeGa, we measured magnetization, Curie temperature, magnetostri…
The structure and thermomagnetic properties of pulsed laser deposited polycrystalline Ni–Mn–Ga alloy films, grown onto thermally oxidized Si(100) wafers, have been investigated. The 300-nm-thick films were deposited at substrate temperatures between 500 and 600 °C from targets made from slices of a Ni2MnGa single crys…
Textured polycrystalline Fe-Ga alloys exhibit magnetostrictive strains of 100 ppm or greater and may function as a mechanically robust actuator/sensing material. Current efforts seek to combine the 300+ ppm magnetostrictive strain performance of [100] oriented single crystals with the mechanical properties of polycrys…
Amorphous silicon nitride (a-SiNx) overcoats are deposited on magnetic disks by rf-reactive sputtering to study their coverage and properties. According to the x-ray photoelectron spectroscopy analysis, a-SiNx has a low coverage-limit of ∼10 Å compared with that of the reference a-CNx (∼20 Å). The lower coverage-limit…
Anomalous positive magnetoresistance (MR) in high temperature organic-based magnet V(TCNE)x (TCNE=tetracynoethylene) thin films is reported. MR increases linearly with applied magnetic field and shows a maximum at the ferrimagnetic ordering temperature. The suggested roles of oppositely spin polarized π* electronic su…
The role of internal stresses on the pyroelectric properties of ferroelectric thin films is analyzed theoretically via a thermodynamic model. The pyroelectric coefficient as a function of the misfit strain is calculated for (001) Ba0.6Sr0.4TiO3 epitaxial thin films. It is shown that this property is highly dependent o…
Polycrystalline ferroelectric thin films of SrBi2Ta2O9 (SBT) and PbZr0.53Ti0.47O3 (PZT) were deposited on Pt/Ti/SiO2/Si substrate by pulsed laser deposition using an eclipse method and the surface potentials were observed by Kelvin probe force microscopy. The data suggest that the surface charge trap is a dominant eff…
Dielectric and magnetic properties of A-site substituted YMnO3 epitaxial films were studied. Stoichiometric epitaxial YMnO3 films clearly show ferroelectric behavior in P–E and C–V measurements. The I–V property is well explained by the Pool–Frenkel-type carrier emission with p-type conduction due to the existence of…