EPR studies of SmBa2Cu3O7-δ/MnFe2O4 superconducting composites

Frontiers in Theoretical and Applied Physics/UAE 2017

Awad, R.^1 ; Isber, S.^2 ; Abou Aly, A.I.^3 ; Abdeen, W.^3 ; El-Tahan, A.^4 ; El-Maghraby, E.M.^5 ; Khalaf, A.^5 ; Noureddine, S.^6

Department of Physics, Faculty of Science, Beirut Arab University, Beirut, Lebanon^1

Department of Physics, Faculty of Science American, University of Beirut, Beirut, Lebanon^2

Department of Physics, Faculty of Science, Alexandria University, Ibrahimia, P.O. Box 426, Alexandria

21321, Egypt^3

Department of Physics, Faculty of Science, Tanta University, Tanta, Egypt^4

Department of Physics, Faculty of Science, Damanhour University, Damanhour, Egypt^5

Department of Physics, Faculty of Science, Lebanese University, Beirut, Lebanon^6

关键词: Composite samples;    Electron paramagnetic resonances (EPR);    Hysteresis measurements;    Local symmetry;    Onset temperature;    Superconducting composites;    Temperature decrease;    Temperature dependence;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/869/1/012033/pdf
DOI  :  10.1088/1742-6596/869/1/012033

来源: IOP

【 摘 要 】

Electron paramagnetic resonance (EPR) studies are carried out on composite samples of SmBa2Cu3O7-δ/(MnFe2O4)xsuperconductors with 0.00 ≤ x ≤ 0.20 wt% at different temperatures 100K ≤ T ≤ 295K. An EPR signal of Cu2+ions in the orthorhombic local symmetry is observed. Moreover, the EPR signal intensity increases as the temperature decreases from room temperature down to 100 K. The temperature dependence of g-factors indicates the pseudogap onset temperature (T∗), corresponding to the peak of the observed curves between 127 K and 162 K. The number of spins (N) participating in EPR resonance are calculated as a function of both nanosized MnFe2O4addition and temperature. In particular, it is shown that any EPR signal for SmBa2Cu3O7-δ/(MnFe2O4)xis probably due to small amount of spurious phases typically present in the samples such as BaCuO2. The presence of BaCuO2is confirmed by magnetization-field (M-H) hysteresis measurements.