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31.
The free carrier absorption (FCA) in a non-degenerate ferromagnetic semiconductor due to electron-two-magnon scattering is calculated below the Curie temperature, assuming a wide conduction band model. It has been found that in EuO FCA due to two-magnon scattering is proportional to λ2·1 (wavelength of radiation) and it has been noticed that for high conductivity samples, explanation of FCA requires the inclusion of ionized impurity scattering of electrons besides the two-magnon process. 相似文献
32.
Krishnamurthy Prasad D.V. Pinjari A.B. Pandit S.T. Mhaske 《Ultrasonics sonochemistry》2010,17(4):697-703
Titanium dioxide was successfully synthesized by utilizing sol–gel technique modified by incorporation of ultrasound as a reaction aid. The effect of amplitude of irradiation (power input varied from 19.9 to 80.8 W) on % Rutile, % yield, % crystallinity, crystallite size and morphological (scanning electron microscopy) properties of the obtained nano-TiO2 was studied. Calcination temperatures of all the samples were kept constant at 750 °C. With increasing ultrasonic irradiation amplitude it is observed that the values of % Rutile (after calcination) increased and reached a peak value after which further increase in amplitude resulted in a decrease in the % Rutile. A similar trend was observed in the case of % crystallinity and % yield of the reaction. On the basis of these results an optimum operating ultrasonic irradiation amplitude for the reaction has been suitably established. 相似文献
33.
34.
Krishnamurthy E. V. Mahadeva Rao T. Subramanian K. 《Proceedings Mathematical Sciences》1975,81(2):58-79
Proceedings - Mathematical Sciences - A fractional weighted number system, based on Hensel’sp-adic number system, is proposed for constructing a unique code (called Hensel’s code) for... 相似文献
35.
The persistent proximity of insulating and metallic phases, a puzzling characteristic of manganites, is argued to arise from the self-organization of the twofold degenerate e(g) orbitals of Mn into localized Jahn-Teller (JT) polaronic levels and broad band states due to the large electron-JT phonon coupling present in them. We describe a new two band model with strong correlations and a dynamical mean-field theory calculation of equilibrium and transport properties. These explain the insulator metal transition and colossal magnetoresistance quantitatively, as well as other consequences of two state coexistence. 相似文献
36.
Boyer RD Johnson R Krishnamurthy K 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,165(2):253-259
Use of adiabatic pulses in broadband inversion and decoupling is well known. Replacement of the rectangular pi pulses in the INEPT and rev-INEPT parts of the HSQC and gHSQC experiments with adiabatic pulses substantially improves the sensitivity of these experiments. However, modulation of cross peak intensity in multiplicity-edited HSQC or gHSQC experiments can be quite severe. These modulations arise during the multiplicity-editing periods due to the inefficient refocusing of the spin-echo caused by the mismatch of the echo delay with the one-bond coupling constant. These modulations (which we call echo modulations) are field strength (and hence spectral width) independent. Use of adiabatic pulses with the inversion sweep synchronized to the 1H-13C coupling constant range typically observed in a 13C spectrum will provide substantial improvement in sensitivity. The inversion profile problems associated with rectangular pi pulses can be moderately compensated by composite pulse schemes and these schemes could prove to be reasonable alternatives to adiabatic pulses. However, the adiabatic sweep provides a unique method to compensate the echo modulations for multiplicity-edited experiments. The origin and the compensation of refocusing inefficiency with synchronized inversion sweep (CRISIS) method to minimize these modulations is described. 相似文献
37.
38.
J. Török S. Krishnamurthy J. Kertész S. Roux 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):697-701
We introduce a model for the slow relaxation of an energy landscape caused by its local interaction with a random walker whose
motion is dictated by the landscape itself. By choosing relevant measures of time and potential this self-quenched dynamics can be mapped on to the “True” Self-Avoiding Walk model. This correspondence reveals that the average distance of
the walker at time t from its starting point is , where for one dimension and 1/2 for all higher dimensions. Furthermore, the evolution of the landscape is similar to that in growth
models with extremal dynamics.
Received 8 August 2000 相似文献
39.
Neha Sharma Bipin K. Srivastava Anjali Krishnamurthy A.K. Nigam 《Solid State Sciences》2010,12(8):1464-1468
Magnetic behaviour of the perovskite La0.5Gd0.5CrO3 has been studied. The orthochromite orders canted antiferromagnetically below Neel temperature TN of ~225 K. Reversal of magnetization is observed in temperature dependence of magnetization measured in field cooled mode under external fields upto 500 Oe. In the field dependence of magnetization below TN, a small hysteresis is observed with the magnetic anisotropy continuously increasing with lowering of temperature. Estimated values of Cr3+ moments, internal field due to sub-lattice of canted ordered Cr3+ and the paramagnetic Curie temperature of Gd3+ sub-lattice are found to be smaller than reported for GdCrO3. Compared with Pr substituted analogue La0.5Pr0.5CrO3, Cr3+ moment is about the same but the internal field at the Gd3+ sub-lattice is much smaller. 相似文献
40.
R. Murugavel G. Anantharaman D. Krishnamurthy M. Sathiyendiran M. G. Walawalkar 《Journal of Chemical Sciences》2000,112(3):273-290
This article describes the recent results obtained in our laboratory on the interaction of polyfunctional ligands with divalent
alkaline earth metal ions and a few divalent transition metal ions. Treatment of MC12·nH2O (M = Mg, Ca, Sr or Ba) with 2-amino benzoic acid leads to the formation of complexes [Mg(2-aba)2] (1), [Ca(2-aba)2(OH2)3]∞ (2), [Sr(2-aba)2(OH2)2
2·H2O)]∞ (3), [Ba(2-aba)2(OH2)]∞ (4), respectively. While the calcium ions in2 are hepta-coordinated, the strontium and barium ions in3 and4 reveal a coordination number of nine apart from additional metal-metal interactions. Apart from the carboxylate functionality,
the amino group also binds to the metal centres in the case of strontium and barium complexes3 and4. Complexes [Mg(H2O)6(4-aba)2·2H2O] (5), [Ca(4-aba)2(H2O)2] (6) prepared from 4-aminobenzoic acid reveal more open or layered structures. Interaction of 2-mercaptobenzoic acid with MCl2·6H2O (M = Mg, Ca), however, leads to the oxidation of the thiol group resulting in the disulphide 2,2′ -dithiobis(benzoic acid).
New metal-organic framework based hydrogen-bonded porous solids [M(btec) (OH2)4
n·n(C4H12N2)·4nH2O] (btec = 1,2,4,5-benzene tetracarboxylate) (M = Co9; Ni10; Zn11) have been synthesized from 1,2,4,5-benzene tetracarboxylic acid in the presence of piperazine. These compounds are made up
of extensively hydrogen-bonded alternating layers of anionic M-btec co-ordination polymer and piperazinium cations. Compounds2- 11 described herein form polymeric networks in the solid-state with the aid of different coordinating capabilities of the carboxylate
anions hydrogen bonding interactions. 相似文献