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

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.