Publications

Electron paramagnetic resonance (EPR) studies are carried out on composite samples of SmBa2Cu3O7-δ/(MnFe2O4)x superconductors 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 MnFe2O4 addition and temperature. In particular, it is shown that any EPR signal for SmBa2Cu3O7-δ/(MnFe2O4)x is probably due to small amount of spurious phases typically present in the samples such as BaCuO2. The presence of BaCuO2 is confirmed by magnetization-field (M-H) hysteresis measurements