Materials Literature
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1-Formyldipyrromethanes are versatile precursors to porphyrins and chlorins. Two methods of synthesis of 1-formyldipyrromethanes have been investigated: (1) Vilsmeier formylation followed by selective removal of the unwanted 1,9-diformyldipyrromethane by dialkyltin complexation and (2) reaction with mesitylmagnesium b…
We fabricated fully epitaxial magnetic tunnel junctions (MTJs) using a Co-based full-Heusler alloy Co2MnGe (CMG) thin film as a lower electrode, an MgO tunnel barrier, and a Co50Fe50 upper electrode and investigated their tunnel magnetoresistance (TMR) characteristics. The microfabricated MTJs showed strongly temperat…
X -band (ν=9.4GHz) electron magnetic resonance (EMR) measurements were carried out in polycrystalline La0.4Ca0.6Mn1−xRuxO3(0⩽x⩽0.16) samples at 100K⩽T⩽550K, aiming to study magnetic/electronic ordering induced by Ru doping. EMR indicates that such doping modifies even the paramagnetic state of La0.4Ca0.6Mn1−xRuxO3 ser…
This paper reports phase components, nanostructure, coercivity mechanism, and hard magnetic properties of FePt and FePt–Ag bulk nanostructured magnets prepared by cyclic cold rolling and subsequent annealing. Annealing temperature of 500 °C or higher and annealing time of 120 min or longer are necessary for the as-rol…
The effect of high pressure on the resonance Raman spectra of the permanganate ion isolated in potassium bromide and potassium perchlorate matrices has been investigated at room temperature for pressures up to 50 kbar. The pressure dependences of the anharmonicity constants and harmonic frequencies have been determine…
Heusler alloy films Co2MnGa grown on ScErAs∕GaAs(001) substrates form stripe domains in the remnant state due to its large strain-induced out-of-plane anisotropy. The dynamics of the stripe domains has been investigated using a microstrip ferromagnetic resonance device in a broad frequency range (∼3–25GHz). In both in…
Electron time-of-flight transient photocurrents from amorphous selenium (a-Se) films were examined over the range of temperatures and applied electric fields in order to deduce a consistent model for the distribution of localized states in the a-Se conduction band tail. Superimposed on an exponential tail with charact…
We report the growth and magnetic properties of BeTe with Cr doping grown on GaAs(001) substrate at Te-rich condition by solid-source molecular-beam epitaxy. Ferromagnetisms were observed for films with high Cr concentration, x. The Curie temperatures TC for x=0.13 and x=0.17 are 175±5K, while the TC for x=0.27 is 250…
A compact magnetometer, which uses two nested 1T Halbach cylinders to generate a variable magnetic field of up to 2T in any direction in the xy plane, has two sets of quadrupole pickup coils to detect the components mx and my of the magnetic moment of a sample vibrating along Oz. Sensitivity is 1.10−7Am2 with integrat…
The L10FePt∕Fe2B-type nanocomposite magnets with high coercivity have been obtained in the Febal.Pt30–32B18–20 alloys directly by the melt spinning technique. The as-spun ribbons showed good hard magnetic properties. The remanence, coercivity, and energy product for the Fe52Pt30B18 alloy melt spun at a wheel circumfer…
Spark plasma sintering technique has been applied to synthesize composite Gdx(Gd5Si2Ge2)1−x (x=0.3, 0.5, and 0.7) with layer structure using high-purity gadolinium (Gd) metal and Gd5Si2Ge2 alloys. The magnetocaloric effect of the composites was studied by directly measuring adiabatic temperature change (ΔTad) with a m…
Planar (2-2) and fibular (1-3) composites were fabricated by embedding single crystal Ni49.9Mn29.1Ga21.0 in a polyurethane resin. Magnetic and mechanical testing was performed on all samples. Mechanical testing showed the twin boundary yield stress to be 1.0 and 0.3MPa for the monolithic and composites, respectively.…
In this work the ferromagnetic state in a ferromagnetic insulating manganite viz. Pr0.8Sr0.2MnO3 was analyzed. The temperature variation of ac susceptibility is seen to show two transitions with a high temperature transition occurring at 158K and a low temperature cusp (Tf) around 90K. The high temperature transition…
Zero-field-cooled and field-cooled magnetization data in single-crystalline Nd0.5Sr0.5MnO3 revealed the existence of thermodynamic irreversibility below Curie temperature (TC), indicating the presence of frustration of spins. The imaginary part of ac susceptibility (χ″) indicates a prominent cusp below TC, which shift…
In this paper, we investigate the magnetization reversal in single-phase RE2Fe14B and two-phase α-Fe∕RE2Fe14B with varying nanoscale grain structures and intergranular exchange interactions produced via controlled segregation during crystallization. We show that the loss of coercivity arises because domain-wall proces…
The light-induced bistability under permanent irradiation (LITH: light-induced thermal hysteresis), due to the competition between light irradiation and self-accelerated relaxation, shows crucially rate-dependent hysteresis. Major and minor hysteresis loops for [Fe(PM-BiA)2(NCS)2] spin crossover compound have been mea…
Time–temperature-transformation diagrams describing the A1 to L10 transformation in 1μm thick FePt and FeCuPt alloy films are constructed from data obtained using nonisothermal differential scanning calorimetry in conjunction with a limited number of isothermal anneals. For the FePt alloys, an increase in Pt content f…
Effects of a TiC addition on microstructure and magnetic properties in [MRE2.2Fe14B](100−2x)∕17.2+TixCx(MRE=Nd+Y+Dy,x=1–5) ribbons, melt spun at a wheel speed of 16m∕s, were systematically studied. X-ray diffraction and differential thermal analysis data revealed that the addition of TiC improves the glass formability…
Variable angle spectroscopic ellipsometry (VASE™) is used as a tool to characterize properties such as optical constant, thickness, refractive index depth profile, and pore volume fraction of single and bilayer porous low-k films. The porous films were prepared using sacrificial pore generator (porogen) approach. Two…
Attempts to fill a wide gap in thermal stability between Nd–Fe–B and Sm–Co based magnets by making a conventional hybrid Nd15Fe79B6∕Sm(Co,Fe,Cu,Zr)7.4 type of magnets encountered two technical difficulties: incompatible processes and interdiffusion between two materials. Because a fundamental change in coercivity mech…