Large magnetodielectric coupling in the vicinity of metamagnetic transition in 6Hperovskite Ba3GdRu2O9

The 6H-perovskites Ba₃RRu₂O₉(R = rare earth element) demonstrate the magnetodielectric (MD) coupling as a manifestation of 4d-4fmagnetic interactions. Here, a detailed study of the structural, magnetic, heat capacity, and MD properties of the 6H-perovskite Ba₃GdRu₂O₉is reported. The signature of long-range antiferromagnetic (AFM) ordering ∼14.8 K (T_N) is evident from the magnetization and heat capacity studies. TheT_Nshifts towards the lower temperature side, apart from splitting in two with the application of the magnetic field. Field-dependent magnetization at 2 K shows three metamagnetic transitions with the opening of small hysteresis in different regions. A new transition atT₁emerges after the onset of the first metamagnetic transition. Complex magnetic behavior is observed in different magnetic field regions whereas these field regions themselves vary with the temperature. Dielectric response recorded at zero and 80 kOe field exhibits the development of MD coupling well aboveT_N. The MD coupling (∼4.5% at 10 K) is enhanced by 25% as compared to the Dy counterpart. Effect of complex magnetic behavior is also conveyed in the MD results where the maximum value of MD coupling is observed in the vicinity of 10 K (onset ofT₁) and near the second metamagnetic transition. Our investigation suggests that both Gd and Ru moments align simultaneously atT_N. Short-range magnetic ordering is possibly responsible for MD coupling aboveT_N.

Structure driven magnetic correlations and magnetodielectric coupling in 6H-perovskite Ba3DyRu2O9

The 6H-perovskites Ba₃(R/M)Ru₂O₉(R= rare Earth,M= transition metal) exhibit complex magnetism and have been extensively studied recently for their magnetodielectric (MD) properties. Here, we present a detailed study of structural, magnetic, thermodynamic and MD properties of a 6H-perovskite Ba₃DyRu₂O₉. This compound is found to undergo long range antiferromagnetic ordering below ∼5.8 K (T_N), along with the presence of metamagnetic transition at low temperatures. The heat capacity shows two additional anomalies at ∼28 K (T₁) and ∼33 K (T₂), besides the anomaly atT_N. Signature of these anomalies is also visible in the derivative of magnetization curve. The dielectric response also shows weak anomalies aroundT₁andT₂at zero field whereas anomaly atT₂gets suppressed at 80 kOe. The observed MD coupling of ∼2%-4% at 80 kOe field below ∼30 K temperature range, is among the highest values observed for the compounds of this family. Low temperature crystal structures of the compound show sharp distortion of Ru₂O₉octahedra nearT₂. Our study points toward the emergence of structurally driven spin correlations of Ru moments resulting in the observed MD coupling in this compound.

Assessment of intracellular Ca2+, cAMP and 1,2-diacylglycerol in cryopreserved buffalo (Bubalus bubalis) spermatozoa on supplementation of taurine and trehalose in the extender

In mammalian spermatozoa, intracellular calcium plays a major role in sperm functions like motility and capacitation. Cryopreservation-induced modifications to sperm membrane result in an influx of intracellular calcium affecting calcium-dependent intracellular signalling pathways. Intracellular calcium activates adenyl cyclase to produce cAMP that activates phospholipase A(2) (PLA(2) ) and phospholipase C (PLC) generating lysophosphatidyl choline, 1,2-diacylglycerol (DAG) and IP(3) , acting as intracellular secondary messengers required for sperm capacitation. Present study was designed to determine levels of intracellular calcium, cAMP and DAG in fresh and frozen-thawed buffalo spermatozoa cryopreserved in the presence and absence of taurine or trehalose. A total number of nine ejaculates from three randomly chosen buffalo bulls were cryopreserved in Tris-based egg yolk extender and thawed in warm water at 37°C. The cAMP was measured by enzyme immuno assay, and intracellular calcium was quantified using fluorescent dye FURA 2-AM. Total lipid was extracted from spermatozoa, and DAG was estimated using thin layer chromatography followed by spectrophotometric analysis. Intracellular calcium, cAMP and DAG levels in spermatozoa were significantly (p < 0.01) increased following cryopreservation as compared to fresh ejaculate. Addition of taurine or trehalose to the freezing medium significantly decreased (p < 0.01) the levels of intracellular calcium and cAMP in frozen-thawed spermatozoa. 1,2-diacylglycerol content was also decreased significantly (p < 0.01) in spermatozoa cryopreserved in presence of additives. Moreover, significant (p < 0.01) improvement in post-thaw motility, viability and membrane integrity of spermatozoa on addition of taurine or trehalose clearly indicated the reduced level of capacitation-like changes in buffalo spermatozoa.