Terahertz-frequency magnetoelectric effect in Ni-doped CaBaCo4O7

We present a study of the terahertz-frequency magnetoelectric effect in ferrimagnetic pyroelectric CaBaCo4O7 and its Ni-doped variants. The terahertz absorption spectrum of these materials consists of spin excitations and low-frequency infrared-active phonons. We studied the magnetic-field-induced changes in the terahertz refractive index and absorption in magnetic fields up to 17 T. We find that the magnetic field modulates the strength of infrared-active optical phonons near 1.2 and 1.6 THz. We use the Lorentz model of the dielectric function to analyze the measured magnetic-field dependence of the refractive index and absorption. We propose that most of the magnetoelectric effect is contributed by the optical phonons near 1.6 THz and higher frequency resonances. Our experimental results can be used to construct and validate more detailed theoretical descriptions of magnetoelectricity in CaBaCo4−xNixO7

ACUTE AND SUBACUTE TOXICITY STUDIES OF ETHANOLIC EXTRACT OF MIRABILIS JALAPA LINN IN WISTAR ALBINO RATS

Objective: The objective of the study was to evaluate the toxicological potential of the ethanolic extract of leaves of Mirabilis jalapa linn through acute and subacute toxicity studies in albino Wistar rats. Methods: For acute toxicity studies, the ethanolic extract of M. jalapa was given up to 2000 mg/kg and then the animals were observed for 14 days to find out any adverse effect or death. For sub-acute toxicity studies, the exact was given for 28 days and the following parameters were observed such as changes in body weight, food intake, water intake, hematological parameters, biochemical parameters, lipid profile, urine analysis, and histopathological studies were undertaken. Results: Single oral administration of 2000 mg/kg of the ethanolic extract of M. jalapa produced no mortality or signs of toxicity. During subacute toxicity there were no changes in body weight, food intake and water intake were observed. There were no changes in lipid profile, hematological parameters, and biochemical parameters. In histopathological changes, there were no structural changes in treated groups when compared to control. Conclusion: The leaves of ethanolic extract of M. jalapa is safe when administered for 28 days. There were no deaths or signs of toxicity in treated rats during acute toxicity studies and subacute toxicity studies

Structural, magnetic and electric-polarization properties of geometrically frustrated YBaCo

In the RBaCo4O7 (R = Ca, Y and rare earth) cobaltite family, only CaBaCo4O7 shows 3D long-range ferrimagnetic and spin-driven electric-polarization properties. In the present study, we have investigated the structural, magnetic and electric polarization properties in YBaCo4O7 and DyBaCo4O7 members of this family and the obtained results are compared with the CaBaCo4O7. The compound YBaCo4O7 showed a series of magnetic transitions in agreement with the reported literature, additionally, a cluster glass behavior below 5 K is observed. Powder neutron diffraction studies on DyBaCo4O7 cobaltite showed an orthorhombic Pbn21 symmetry and signature of short-range 120° magnetic correlations of kagome layer and a spin glass behavior below 65 K. Dielectric measurements on both the samples showed strong frequency dispersion at high-temperature and frequency-independent behavior at low temperature without dielectric anomaly. Pyroelectric current measurement has showed a broad peak around 50 K in both the samples; however, a careful analysis relates the peak to thermally stimulated depolarization current. This study signifies that the giant structural distortions and cobalt charge ordering at the kagome layer are the key factors to drive both long-range magnetic ordering and spin-driven electric polarization in this cobaltite family

Switching from pyroelectric to ferroelectric order in Ni-doped CaBaCo4O7

We report ferroelectric ordering in Ni-substituted CaBaCo4O7. Magnetization showed ferrimagnetic transition at 60 K and an additional magnetic anomaly is found at similar to 82 K. The enhanced antiferromagnetic interactions and decrease in saturation magnetization are noticed with Ni substitution. The dielectric and pyroelectric measurements illustrate strong coupling between spin and charge degrees of freedom. Ferroelectric behavior is confirmed with enhanced ordering temperature (similar to 82 K) and saturation polarization (250 mu C/m(2)). Neutron diffraction has revealed an increase in c-lattice parameter in the Ni sample. All the Co/Ni moments are reoriented in the a direction. A transition from a noncollinear ferrimagnetic to a collinear ferrimagnetic spin order, with up arrow up arrow down arrow down arrow antiferromagnetic ordering in the kagome layer, is observedwith substitution. This results in the appearance of unequal bond distances in a two-dimensional collinear layer; most likely this is responsible for the transition from pyroelectric to ferroelectric, with the possibility of switching of electric polarization