Multiple magnetic transitions and magnetocaloric effect in Gd1-xSmxMn2Ge2 compounds

Magnetic and magnetocaloric properties of polycrystalline samples of Gd1-xSmxMn2Ge2 have been studied. All the compounds except GdMn2Ge2 show re-entrant ferromagnetic behavior. Multiple magnetic transitions observed in these compounds are explained on the basis of the temperature dependences of the exchange strengths of the rare earth and Mn sublattices. Magnetocaloric effect is found to be positive at the re-entrant ferromagnetic transition, whereas it is negative at the antiferro-ferromagnetic transition. In SmMn2Ge2, the magnetic entropy change associated with the re-entrant transition is found to decrease with field, which is attributed to the admixture effect of the crystal field levels. The isothermal magnetic entropy change is found to decrease with increase in Sm concentration.Comment:

Heat capacity and magnetocaloric effect in polycrystalline Gd1-xSmxMn2Si2

We report the magnetocaloric effect in terms of isothermal magnetic entropy change as well as adiabatic temperature change, calculated using the heat capacity data. Using the zero field heat capacity data, the magnetic contribution to the heat capacity has been estimated. The variations in the magnetocaloric behavior have been explained on the basis of the magnetic structure of these compounds. The refrigerant capacities have also been calculated for these compounds

Phenomenology and diagnoses associated with psychogenic non-epileptic seizures

Introduction: Psychogenic non-epileptic seizures (PNES) are seizure resembling behavior without electrical correlates insidethe brain, often having a psychogenic etiology. However, there is a paucity of research into the phenomenology, and hence,there is frequent diagnostic dilemma. The phenomenology appears to be spread across multiple diagnostic categories in nonspecificmanner. The study aimed at finding the phenomenology and the other diagnoses associated with PNES. Materials andMethods: 50 consecutive patients presenting to the tertiary psychiatric center of Eastern India were enquired on semi-structuredproforma to assess the phenomenology (including the antecedent events or stressors, ictal details, and the post-ictal stage) andassociated diagnosis. Appropriate diagnostic tools were used to verify the associated diagnoses. Results: The patients of thissample mostly belonged mostly to low socioeconomic group, females from second decade who were unemployed and had poorsocioeconomic support. They mostly had ongoing stressors, were mute during spells showed non-stereotyped movements of bodyparts. Most of them also had other Axis I and Axis II diagnosis of which depression, anxiety, and personality disorder were common.Conclusion: PNES is a non-specific expression of various underlying psychopathologies, because it is seen most often with otherindependently diagnosable psychiatric conditions

Role of the dielectric constant of ferroelectric ceramic in enhancing the ionic conductivity of a polymer electrolyte composite

The dispersal of high dielectric constant ferroelectric ceramic material Ba(0.7)Sr(0.3)TiO(3) (Tc~30 C) and Ba(0.88)Sr(0.12)TiO(3) (Tc~90 C) in an ion conducting polymer electrolyte (PEO:NH4I) is reported to result in an increase in the room temperature ionic conductivity by two orders of magnitude. The conductivity enhancememt "peaks" as we approach the dielectric phase transition of the dispersed ferroelectric material where the dielectric constant changes from ~ 2000 to 4000. This establishes the role of dielectric constant of the dispersoid in enhancing the ionic conductivity of the polymeric composites.Comment: 10 pages, 2 figure

Effect of Ge substitution for Si on the anomalous magnetocaloric and magnetoresistance properties of GdMn2Si2 compounds

The effect of Ge substitution on the magnetization, heat capacity, magnetocaloric effect and magnetoresistance of GdMn2Si2-xGex (x=0, 1, and 2) compounds has been studied. The magnetic transition associated with the Gd ordering is found to change from second order to first order on Ge substitution. Magnetic contributions to the total heat capacity and the entropy have been estimated. Magnetocaloric effect has been calculated in terms of adiabatic temperature change (deltaTad) as well as isothermal magnetic entropy change (deltaSM) using the heat capacity data. The temperature dependence of the magnetocaloric effect in all the three compounds have shown broad peaks. The maximum values of deltaSM and deltaTad for GdMn2Ge2 are found to be 5.9 J/kgK and 1.2 K, respectively. The magnetoresistance is found to be very large and positive with a maximum value of about 22% in the case of GdMn2Ge2. In the other two compounds also, the magnetoresistance is predominantly positive, except in the vicinity of the Gd ordering temperature. The anomalous nature of the magnetocaloric effect and the magnetoresistance has been attributed to the canted magnetic structure of these compounds