A study of the ferromagnetic transition of $SrRu{O}_3$ in nanometer thick bilayers with $YB{a}_{2}C{u}_3{O}_y$, $L{a}_{1.88}S{r}_{0.12}Cu{O}_{4-y}$, Au and Cr: Signature of injected carriers in the pseudogap regime

Abstract

The hypothesis regarding the existence of uncorrelated pre-formed pairs in the pseudogap regime of superconducting $YB{a}_{2}C{u}_3{O}_y$ is tested experimentally using bilayers of $YB{a}_{2}C{u}_3{O}_y$ and the itinerant ferromagnet $SrRu{O}_3$. In our study, we monitor the influence of $YB{a}_{2}C{u}_3{O}_y$ on $T_p$, the ferromagnetic ordering temperature of $SrRu{O}_3$. Here, $T_p$ is the temperature of maximum dM/dT or dR/dT where M and R are the magnetization and resistance of $SrRu{O}_3$, respectively. We compare the results with similar measurements carried out on bilayers of $L{a}_{1.88}S{r}_{0.12}Cu{O}_{4-y}$, $Au$ and $Cr$ with $SrRu{O}_3$. We find that in bilayers made of underdoped 10 nm $YB{a}_{2}C{u}_3{O}_y$/5 nm $SrRu{O}_3$, the $T_p$ values are shifted to lower temperatures by up to 6-8 K as compared to $T_p\approx 140$ K of the 5 nm thick reference $SrRu{O}_3$ film. In contrast, in the other type of bilayers, which are not in the pseudogap regime near $T_p$, only a smaller shift of up to $\pm$2 K is observed. These differences are discussed in terms of a proximity effect, where carriers from the $YB{a}_{2}C{u}_3{O}_y$ layer are injected into the $SrRu{O}_3$ layer and vice versa. We suggest that correlated electrons in the pseudogap regime of $YB{a}_{2}C{u}_3{O}_y$ are responsible for the observed large $T_p$ shifts.

9 figures

References in corpus (1)

• Scanning tunneling spectroscopy characterization of the pseudogap and the x = 1/8 anomaly in La2-xSrxCuO4 thin films