Magnetotransport properties and pseudogap phase diagram of superconducting EuBa2Cu3Oy thin films: the influence of Eu substitution

This research explores and debates magnetotransport properties and the pseudogap phase diagram of high-temperature superconducting EuBa(2)Cu(3)Oy (EBCO) films through rho(xx) (T) and rho(xy) (T) measurements. The mixed state transport properties of samples with higher doped levels show a power-law field-dependence of activation energyU, U proportional to H (alpha) with alpha =. 0.52 +/- 0.05, while the slightly doped samples reveal a logarithmic field-dependence ofU. In addition, for the first time, all samples in the underdoped region display an unusual power-law behavior of U proportional to p(gamma) with gamma = -5.90 +/- 0.28, which is qualitatively explained. A sign reversal of transverse resistivity in the mixed state is also present in the nearly optimum-doped samples, which have strong pinning energies. In the normal state, the cotangent of the Hall angle shows a wide range quadratic temperature dependence for all the samples, which can be described by Anderson's theory. The values of spin excitation bandwidthWare coincident between two results obtained from the hidden Fermi-liquid theory and from the Hall angle for the slightly overdoped sample. Moreover, the phase diagram of EBCO, containing the superconducting transition temperatures, the T* and T** temperatures in the pseudogap (PG) phase, and the antiferromagnetic transition temperatures theta(N), in the whole underdoped region has been completed and compared with those for YBa(2)Cu(3)Oy (YBCO). The findings demonstrate that EBCO has lower T* and T** values, versus those of YBCO in the same doping region. The observed smaller magnitude of PG for EBCO is explained by considering the oxygen vibrational amplitudes in Cu-O-Cu bonds, which agrees with the inference based on the fluctuating bond model. The influence of Eu substitution is examined and discussed.