Role of Crystal Field in Mixed Alkali Metal Effect: Electron Paramagnetic Resonance Study of Mixed Alkali Metal Oxyfluoro Vanadate Glasses

2014 ◽  
Vol 118 (3) ◽  
pp. 573-578 ◽  
Author(s):  
Gajanan V. Honnavar ◽  
K. P. Ramesh ◽  
S. V. Bhat
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Alkali Metal ◽  
Crystal Field ◽  
Electron Paramagnetic Resonance Study ◽  
Paramagnetic Resonance ◽  
Mixed Alkali ◽  
Electron Paramagnetic ◽  
Vanadate Glasses ◽  
Metal Effect

Single crystal electron paramagnetic resonance study of Y2BaCuO5, a common impurity in the high temperature superconductor, YBa2Cu3O7

1992 ◽  
Vol 7 (3) ◽  
pp. 565-571 ◽  
Author(s):  
R.J. Barham ◽  
D.C. Doetschman
Keyword(s):  
Crystal Structure ◽  
Electron Paramagnetic Resonance ◽  
Single Crystal ◽  
Crystal Field ◽  
Electron Paramagnetic Resonance Study ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Crystal Forms ◽  
Crystal Electron ◽  
Electron Paramagnetic

Electron paramagnetic resonance (EPR) studies of pure Y2BaCuO5 in powder and single crystal forms and of YBa2Cu3O7−δ in powder and single crystal forms provide further evidence that it is Y2BaCuO5 that is the common green impurity found in many preparations of YBa2Cu3O7−δ as a powder or in pellet forms. Y2BaCuO5 tends to be excluded in the growth of YBa2Cu3O7−δ single crystals. A method is presented for the growth of Y2BaCuO5 crystals from a flux. An apparent discrepancy between the observed single crystal EPR anisotropy and the reported crystal structure is resolved in three independent ways from the Y2BaCuO5 Powder and single crystal EPR data. These results show that the EPR spectrum is a superposition of the spectra of the two differently oriented Cu sites in the unit cell and is not a spectral average of them. The temperature independence of the EPR spectrum between 150 K and 300 K is also consistent with there being no temperature dependent exchange averaging of the EPR spectra of the two sites in this range. The orientations of the Cu crystal field axes, as indicated by the g axes, are in agreement with the crystal structure. Crystal field splittings of the Cu d-orbitals are estimated from the measured g values and indicate an appreciable covalency in the Cu–O bonds. The linewidth and its anisotropy indicate a minor degree of exchange narrowing.

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