An investigation of the spin-Hamiltonian parameters for Gd³⁺-doped YBa₂Cu₃O_6+y(y= 0.06) superconductor

Abstract

The spin-Hamiltonian parameters (g factors g∥ and g⊥ and zero-field splittings , , , and ) for Gd3+ ions at the tetragonal Y3+ site of YBa2Cu3O6+y (y = 0.06) superconductor are calculated together from a diagonalization (of the energy matrix) method based on the one-electron crystal field mechanism. In the method, a 56 × 56 energy matrix concerning the ground multiplet 8S7/2 and the excited multiplets 8L7/2 (where L = P, D, F, G, H, I) for 4f7 ions at a tetragonal crystal field and under an external magnetic field is constructed and used. The crystal field parameters in the energy matrix are obtained from the superposition model. The calculated results are in reasonable agreement with the experimental values. The defect structure (characterized by the angular distortion Δθ) of the Gd3+ impurity centers in YBa2Cu3O6+y is also acquired from the calculation. The results are discussed.

Isolation, Absolute Configuration, and Biological Activities of Chebulic Acid and Brevifolincarboxylic Acid Derivatives fromEuphorbia hirta

“…Euphorbia hirta Linn. (Euphorbiaceae), which is widely distributed in South China, India, and the Southeastern Asia region, have been extensively used in folk medicine to treat chronic bronchitis and respiratory diseases. , This plant was reported to contain a variety of compounds, such as flavonoids, diterpenoids, triterpenoids, and other constituents. , Owing to its significant bioactivities and in our continuing search for diverse structures of natural products from traditional Chinese medicines, the chemical constituents of E. hirta have been investigated. Twenty new compounds, including 17 chebulic acid derivatives ( 1 – 7 and 8a / 8b – 12a / 12b ) and three brevifolincarboxylic acid derivatives ( 13a / 13b and 14 ), and nine known analogues ( 15 – 23 ), were isolated from the aerial parts of E. hirta .…”