Relations between structural distortions and transport properties in Nd0.5_{0.5}Ca0.5_{0.5}MnO3_3 strained thin films

Strained thin films of charge/orbital ordered (CO/OO) $Nd_{0.5}Ca_{0.5}MnO_3$ (NCMO) with various thickness have grown on (100)-SrTiO$_3$ and (100)-LaAlO$_3$ substrates, by using the Pulsed Laser Deposition (PLD) technique. The thickness of the films influences drastically the transport properties. As the thickness decreases, the CO transition increases while at the same time the insulator-to-metal transition temperature decreases under application of a 7T magnetic field. Clear relationships between the structural distortions and the transport properties are established. They are explained on the basis of the elongation and the compression of the Mn-O-Mn and Mn-O bond angles and distances of the \QTR{it}{Pnma} structure, which modify the bandwidth and the Jahn-Teller distortion in these materialsComment: 11 pages, 6 figures. to be published in Journal Physics: Condensed Matte

ANTI-DIABETIC EFFECT OF POLYHERBAL FORMULATION IN OGTT AND STREPTOZOTOCIN-INDUCED DIABETIC RAT MODEL

Objective: The present study investigates the efficacy of DiaKure, a poly herbal formulation composed of powder of different herbs on blood glucose level of normal and diabetic rats.Methods: The raw materials were collected made it into a powder formulation. Streptozotocin 60 mg/kg was administered as a single i. p. Injection for induction of type 1 diabetes. After one week of streptozotocin injection, animals showing glycosuria (fasting blood sugar level>200 mg/dL) were considered as diabetic. The hypoglycemic activity and glucose tolerance test were studied in normal and Streptozotocin-induced diabetic rats after administration of DiaKure at a dose of 300 mg/kg. Blood glucose was determined by a glucose monitor.Results: At a dose of 200 and 300 mg/kg p. o., DiaKure showed a hypoglycemic effect at a varying degree of significance (P<0.05-0.001) in normal rats in comparison with the respective control group. Maximum effect of DiaKure treatment in the glucose tolerance test occurred at 120thminute of glucose administration in normal rats.Conclusion: The results indicate significant hypoglycemic activity of DiaKure in male albino rats.Â

Local structural changes in paramagnetic and charge ordered phases of Sm0.2Pr0.3Sr0.5MnO3: An EXAFS Study

Sm{0.5-x}Pr{x}Sr{0.5}MnO{3} exhibits variety of ground states as x is varied from 0 to 0.5. At an intermediate doping of x = 0.3 a charge-ordered CE type antiferromagnetic insulating (AFI) ground state is seen. The transition to this ground state is from a paramagnetic insulating (PMI) phase through a ferromagnetic metallic phase (FMM). Local structures in PMI and AFI phases of x = 0.3 sample have been investigated using Pr K-edge and Sm K-edge Extended X-ray Absorption Fine Structure (EXAFS). It can be seen that the tilting and rotation of the MnO6 octahedra about the b-axis are responsible for the charge ordered CE-type antiferromagnetic ground state at low temperatures. In addition a shift in the position of the rare earth ion along the c-axis has to be considered to account for observed distribution of bond distances around the rare earth ion

Structural and doping effects in the half-metallic double perovskite A2A_2CrWO6_6

he structural, transport, magnetic and optical properties of the double perovskite $A_2$CrWO$_6$ with $A=\text{Sr, Ba, Ca}$ have been studied. By varying the alkaline earth ion on the $A$ site, the influence of steric effects on the Curie temperature $T_C$ and the saturation magnetization has been determined. A maximum $T_C=458$ K was found for Sr$_2$CrWO$_6$ having an almost undistorted perovskite structure with a tolerance factor $f\simeq 1$. For Ca$_2$CrWO$_6$ and Ba$_2$CrWO$_6$ structural changes result in a strong reduction of $T_C$. Our study strongly suggests that for the double perovskites in general an optimum $T_C$ is achieved only for $f \simeq 1$, that is, for an undistorted perovskite structure. Electron doping in Sr$_2$CrWO$_6$ by a partial substitution of Sr$^{2+}$ by La$^{3+}$ was found to reduce both $T_C$ and the saturation magnetization $M_s$. The reduction of $M_s$ could be attributed both to band structure effects and the Cr/W antisites induced by doping. Band structure calculations for Sr$_2$CrWO$_6$ predict an energy gap in the spin-up band, but a finite density of states for the spin-down band. The predictions of the band structure calculation are consistent with our optical measurements. Our experimental results support the presence of a kinetic energy driven mechanism in $A_2$CrWO$_6$, where ferromagnetism is stabilized by a hybridization of states of the nonmagnetic W-site positioned in between the high spin Cr-sites.Comment: 14 pages, 10 figure

Influence of B - site Disorder in La0.5Ca0.5Mn1−xBxO3La_{0.5}Ca_{0.5}Mn_{1-x}B_{x}O_{3} (B = Fe, Ru, Al and Ga) Manganites

We have investigated the influence of B - site doping on the crystal and magnetic structure in $La_{0.5}Ca_{0.5}Mn_{1-x}B_{x}O_{3}$ (B= Fe, Ru, Al and Ga) compounds using neutron diffraction, SANS, magnetization and resistivity techniques. The B - site doped samples are isostructural and possess an orthorhombic structure in \textit{Pnma} space group at 300K. A structural transition from orthorhombic to monoclinic is found to precede the magnetic transition to CE - type antiferromagnetic state in few of these samples. On doping with Fe, charge and orbitally ordered CE - type antiferromagnetic state is suppressed, followed by the growth in ferromagnetic insulating phase in $0.02\leq x\leq0.06$ compounds. At higher Fe doping in $x>0.06$, the ferromagnetic state is also suppressed and no evidence of long range magnetic ordering is observed. In Ru doped samples $(0.01\leq x\leq0.05)$, the ferromagnetic metallic state is favored at $T{}_{C}\approx200K$ and $T_{MI}\approx125K$ and no significant change in $T_{C}$ and $T_{MI}$ as a function of Ru doping is found. In contrast, with non magnetic Al substitution for $0.01\leq x\leq0.03$, the charge ordered CE - type antiferromagnetic state coexists with the ferromagnetic metallic phase. With further increase in Al doping $(0.05\leq x\leq0.07)$, both CE - type antiferromagnetic and ferromagnetic phases are gradually suppressed. This behavior is accompanied by the evolution of A - type antiferromagnetic insulating state. Eventually, at higher Al doping $(0.10\leq x\leq0.13)$, this phase is also suppressed and signature of spin glass like transition are evident in M(T). Likewise, substitution with Ga is observed to induce similar effects as described for Al doped samples. The presence of short ranged ferromagnetic ordering has been further explored using SANS measurements in few of the selected samples.Comment: To appear in Journal of Physics: Condensed Matte

Metal Halide Complexes of Quinoline N-Oxide: A Study of Halide Interaction in the Coordination of Neutral Monodentate Ligand

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Cost of cultivation components of production of oil palm fresh fruit bunches per tonneOil palm (Elaeis guineensis) is cultivated in an area of 2.3 lakh ha across 11 states in India (Ravichandran et al., 2014). Andhra Pradesh, Karnataka, Tamil Nadu, Mizoram and Kerala are the major oil palm growing states in the country, of which Andhra Pradesh alone has a share of more than 65 per cent in area under the crop (Ravichandran et al., 2014). This perennial crop has an economic life span of about 30 years, comprising of three distinct phases viz., juvenile period (1-3 years), yield stabilizing period (4-8 years) and stabilized yield period (9-30 years). The economic part of oil palm is bunch of fruits which are commonly referred as Fresh Fruit Bunch (FFB). From this FFB, crude palm oil is extracted from mesocarp and palm kernel oil is extracted from palm kernels. Oil palm is having the pride of giving highest oil yield per unit area (4-6 tonnes of oil ha-1) among all the oil seed crops of the world. Under the present agricultural scenario, in which farmers generally feel that the profitability from farming is declining, it is important to assess the economics of cultivation of any crop. This is true in case of perennial crops, where farmers invest their assets i.e., land, irrigation, manpower etc. for more than three decades and the major decisions taken are irrevocable. Estimation of cost of cultivation of perennial crops or their farming systems were earlier done both under optimum management conditions (research conditions) as well as under farmer’s field conditions (Sairam et al., 1997; 1999; 2004; Maheshwarappa et al., 2000; Ray et al., 2000). Kalidas et al. (2011) estimated the scientific formula for fixing support price for oil palm through estimation of cost of production as well as processing. The overall objective of the paper is to estimate various cost components involved in cost of cultivation of oil palm under farmer’s field condition and to estimate the cost of production of one tonne of oil palm FFBICA