Magnetic and the magnetocaloric properties of Ce1-xRxFe2 and Ce(Fe1-xMx)2 compounds

We have studied selected rare earth doped and transition metal doped CeFe2 compounds by examining their structural, magnetic and magneto-thermal properties. With substitution of Ce by 5 and 10% Gd and 10% Ho, the Curie temperature can be tuned to the range of 267-318 K. Localization of Ce 4f electronic state with rare earth substitutions is attributed for the enhancement of Curie temperature. On the other hand, with Ga and Al substitution at the Fe site, system undergoes paramagnetic to ferromagnetic transition and then to an antiferromagnetic phase on cooling. The magnetocaloric effect across the transitions has been studied from both magnetization isotherms and heat capacity data. It is shown that by choosing the appropriate dopant and its concentration, the magnetocaloric effect around room temperature can be tuned.Comment: 13 pages, 6 figures, 2 table

Marshall-Smith syndrome: a distinct entity

This article does not have an abstract

Development of an Advanced Engineering Polymer from the Modification of Nylon 66 by e-Beam Irradiation

When Nylon 66 was irradiated by an optimum dose of e-beam in presence of polyurethane as impact modifierin combination with triallyl isocyanurate as cross-linker, a superior performance was observed for the irradiatednylon 66. Significant improvement of properties, such as hardness, tensile strength, flexural modulus and impactstrength was obtained on radiation processing of nylon 66 by e-beam. More interestingly, percent water absorptionof such irradiated nylon 66 was reduced substantially. Improvement of mechanical properties and reduction of waterabsorption of irradiated nylon 66 were due to the cross-linking of the polymer system. Increase of cross-linkingwith dose of e-beam was verified by the increased gel content at higher doses. Irradiated nylon 66 showed betterdimensional stability than those achieved with pristine nylon 66. The increase in dimensional stability may beattributed to reduction in crystallinity with increasing dose of e-beam as revealed by DSC studies.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 281-289, DOI:http://dx.doi.org/10.14429/dsj.64.732

Stabilization of antiferromagnetism in CeFe2 alloys: Effects of chemical and hydrostatic pressure

Effects of Al, Mn and Sb dopings in CeFe2 and effect of applied pressure have been investigated. Al doping gives rise to the FM-AFM transition and a reduction in the magnetic moment and TC values, clearly indicating the growth of the AFM component. Mn and Sb dopings only cause a reduction in TC value. It is found that in general external pressure enhances the antiferromagnetism in both the pure and the doped alloys. Enhancement of the Ce 4f- Fe 3d hybridization as a result of dopings and with the external pressure may be the reason for the stabilization of antiferromagnetism in these alloys.Comment: 14 pages, 7 figure

Free-carrier-driven Kerr frequency comb in optical microcavities: Steady state, bistability, self-pulsation, and modulation instability

Continuous-wave pumped optical microresonators have been vastly exploited to generate a frequency comb (FC) utilizing the Kerr nonlinearity. Most of the nonlinear materials used to build photonic platforms exhibit nonlinear losses such as multiphoton absorption, free-carrier absorption, and free-carrier dispersion which can strongly affect their nonlinear performances. In this work, we model the Kerr FC based on a modified Lugiato-Lefever equation (LLE) along with the rate equation and develop analytical formulations to make a quick estimation of the steady state, bistability, self-pulsation, and modulation instability (MI) gain and bandwidth in the presence of nonlinear losses. The analytical model is valid over a broad wavelength range as it includes the effects of all nonlinear losses. Higher-order (>3)characteristic polynomials of intracavity power describing the steady-state homogeneous solution of the modified LLE are discussed in detail. We derive the generalized analytical expressions for the threshold (normalized) pump detuning that initiates the optical bistability when nonlinear losses are present. Free-carrier dispersion-led nonlinear cavity detuning is observed through the reverse Kerr tilt of the resonant peaks. We further deduce the expressions of the threshold pump intensity and the range of possible cavity detuning for the initiation of the MI considering the presence of nonlinear losses. The proposed model will be helpful in explaining several numerical and experimental results which have been previously reported and thereby will be able to provide a better understanding of the comb dynamics

Ultrasonic pulse induced mechanoluminescence of europium doped strontium aluminate micro-crystals

When rare earth doped strontium aluminate micro-crystals are exposed to ultrasonic pulse, then mechanumnescence (ML) is induced. The intensity of ML is proportional to the power of ultrasonic pulse used for ML excitation. The ML in europium doped strontium aluminate micro-crystals can be understood on the basis of the piezoelectrically induced electron detrapping model. On the basis of the piezoelectrically-induced electron detrapping model, expressions are derived for the general kinetics of ML intensity, rise of ML intensity, peak ML intensity and decay of ML intensity, in which good agreement is found between the theoretical and experimental results. A linear relation between the ML intensity and the ultrasonic power can also be understood on the basis of the proposed theory. The present investigation shows that the ML can be used to detecting the presence of ultrasonic waves and also for the measurement of ultrasonic power.&nbsp