The Effects of Chemical Doping on the Diamagnetic Thermodynamic Fluctuations of YBa2Cu2.97X0.03O7-δ (X = Au, Ni, Zn, and Mg) Single Crystals

摘要

In this article, we investigated the effects of chemical doping on the diamagnetic thermodynamic fluctuations (DTFs) of YBa ₂ Cu _2.97 X _0.03 O $_{7-delta}$ (X = Au, Ni, Zn, and Mg) single crystals. In-plane dc zero field cooled [ $M_{mathrm {ZFC}}(T)$ ] and field cooled cooling [ $M_{mathrm {FCC}}(T)$ ] magnetizations were measured with a superconducting quantum interference device (SQUID) magnetometer while magnetic fields ( $H$ ) ranging from 0.01 up to 50 kOe were applied. The DTF contribution on the reversible $M_{mathrm {ZFC}}(T)$ magnetization was accounted by applying 3D-XY and 3-D lowest Landau level (3D-LLL) scaling functions. The results show that the DTF contribution on the reversible $M_{mathrm {ZFC}}(T)$ data of our samples is well described by the 3D-XY scaling function when $H le 1$ kOe (low-magnetic-field regime) is applied and by the 3D-LLL scaling function when $H > 10$ kOe (high-magnetic-field regime) is applied. The reversible $M_{mathrm {ZFC}}(T)$ data of the doped samples display in the low-magnetic-field regime a rounded of the DTF regime around $T_{mathrm {C}}$ and a temperature enlargement of the DTF regime range in the high-magnetic-field regime. We believe that these effects are connected to intensification of YBa ₂ Cu ₃ O $_{7-delta}$ inhomogeneous superconducting state caused by individual partial substitution of ≈1% of Cu for chemical dopants listed above.