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(Ni48Co6)Mn26Al20 polycrystalline ribbons with B2 structure at room temperature are investigated. Considering the presence of competing magnetic interactions, Arrott-plot analysis gives TN ∼ 170 K. A broad ferromagnetic-paramagnetic transition (TC) is observed at ∼200 K. H-T phase-diagram is used to validate the presence of competing exchange interactions that persist till very close to TC. Based on Néel theory, a cluster model is used to explain the presence of ferromagnetic and antiferromagnetic clusters in the sample. Formation of ferromagnetic clusters can be understood in terms of positive exchange interactions among the Mn atoms that are neighboring Co atoms located at Ni sites. [ABSTRACT FROM AUTHOR]

The spin forbidden transition a1Δ → X3Σ- in CH- has been studied using the Breit-Pauli Hamiltonian for a large number of geometries. This transition acquires intensity through spin-orbit coupling with singlet and triplet Π states. The transition moment matrix including more than one singlet and triplet Π states was calculated at the multi-reference configuration interaction/aug-cc-pV6Z level of theory. The computed radiative lifetime of 5.63 s is in good agreement with the experimental (5.9 s) and other theoretical (6.14 s) results. Transition moment values of the spin allowed A3Π → X3Σ- transition have also been calculated at the same level of theory. Calculations show that the corresponding radiative lifetime is considerably low, 2.4 × 10-7 s. Complete basis set extrapolated potential energy curves for the ground state of CH and the ground state and six low lying excited states (a1Δ, b1Σ+, two 3Π, and two 1Π) of CH- are reported. These curves are then used to calculate the vibrational bound states for CH and CH-. The computed electron affinity of CH supports the electron affinity bounds reported by Okumura et al. [J. Chem. Phys. 85, 1971 (1986)]. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and transport properties of Ni52+xMn26-xAl22 (1 ≤ x ≤ 5) melt-spun ribbons have been characterized by a variety of experimental techniques. As the composition changed from x = 1 to x = 5, the martensitic transition temperature T0 [ = (Ms + Af)/2] was found to increase from 277 K to 446 K which was attributed to an increase in the valence electron concentration e/a. In the martensitic state, all the samples demonstrate an anomalous semiconducting behavior of electrical resistivity ρ. This uncommon feature of the transport properties has been ascribed to the existence of a gap (Eg ∼ 0.1 eV) at the Fermi level. A crossover from semiconducting to metallic behavior of ρ observed in the martensitic state of Ni57Mn21Al22 is presumably related to a spin-density wave formation at the Neel temperature TN ≈ 300 K. Analysis of a low-temperature (T < 60 K) part of the resistivity curves and comprehensive magnetic measurements of a Ni57Mn21Al22 (x ≤ 5) sample provide grounds for the conclusion that the splitting of zero-field cooling and field cooling magnetization curves observed at low temperatures is due to a spin-glass state that is formed below the freezing temperature Tf. [ABSTRACT FROM AUTHOR]

We report results of studies relating to the fabrication of a microfluidics cholesterol sensor based on nanocrystalline anatase-titanium dioxide (ant-TiO2) film deposited onto indium tin oxide (ITO) glass. The results of response studies (optimized under the flow rate of 30 μl/min) conducted on cholesterol oxidase (ChOx) immobilized onto crystalline ant-TiO2 nanoparticles (∼27 nm)/ITO microfluidics electrode reveal linearity as 1.3 to 10.3 mM and improved sensitivity of 94.65 μA/mM/cm2. The observed low value of Km (0.14 mM) indicates high affinity of ChOx to cholesterol. No significant changes in current response of this microfluidics sensor are measured in the presence of different interferents. [ABSTRACT FROM AUTHOR]

Results of fundamental and third order ac susceptibility measurements in a Ni49Mn29Ga22 single crystal demonstrate that higher harmonics of ac-susceptibility measurement is an excellent tool to identify transitions/anomalies originating from different magnetic substructures that remain undetected by usual dc susceptibility measurements. Anomaly observed at low temperature (∼150 K) has also been explored by differential scanning calorimetry, temperature dependent x-ray diffraction, and transmission electron microscopy measurements. The results demonstrate that the magnetic subsystem in Ni-Mn-Ga is unstable at low temperatures not only for metastable modulated crystal structure but also for very stable nonmodulated tetragonal structure. [ABSTRACT FROM AUTHOR]

Magnetic and structural properties of Ni–Mn–Al thin films are investigated. It is demonstrated that the annealed film shows L21 phase at room temperature. Magnetometry measurements reveal that the annealed film is ferromagnetic and a first order transition in magnetization versus temperature measurement confirms that the martensite to austenite transition occurs around room temperature. Transmission electron microscopy measurements confirm that this structural change occurs just below room temperature. The splitting of Mn 2p3/2 level in x-ray photoelectron spectroscopy core level spectra of the annealed Ni–Mn–Al film, confirms that the origin of magnetism is definitely correlated with the local magnetic moment at the Mn atoms. [ABSTRACT FROM AUTHOR]

Effect of varying particle size and maximum applied field during initial magnetization (HM) on zero-field cooled (ZFC) exchange bias (EB) in hexagonal YMnO3 nanoparticles prepared by conventional solid state method has been studied. EB phenomenon is observed after ZFC from an unmagnetized state without any remanent magnetization. EB field (Heb) and Vertical shift (ME) were found to vary nonmonotonically with both particle size and HM. Large Heb of 1024 Oe is obtained for the particle size of 55 nm. These features are attributed to the exchange interaction between the compensated antiferromagnetic spins and uncompensated surface spins of the nanoparticles. [ABSTRACT FROM AUTHOR]