Element-specific probe of Ru magnetism and local structure in ${\text{RuSr}}_2{\text{Eu}}_{1.5}{\text{Ce}}_{0.5}{\text{Cu}}_2{\text{O}}_{10}$

Element-specific x-ray magnetic circular dichroism measurements at the $\text{Ru}{L}_3$ absorption edge are used to search for the presence of a net Ru ferromagnetic moment in the superconducting state of ${\text{RuSr}}_2{\text{Eu}}_{1.5}{\text{Ce}}_{0.5}{\text{Cu}}_2{\text{O}}_{10}$. A net moment of $0.21{\mu }_B/\text{Ru}$ is observed in zero applied field. Together with a homogeneous Ru local structure probed by x-ray absorption fine-structure measurements, the results unequivocally demonstrate the coexistence of a ferromagnetic component in the magnetically ordered ${\text{RuO}}_2$ planes with superconductivity in the ${\text{CuO}}_2$ planes.

Figure 1

(Color online) (a) Main panel: magnetic moment per formula unit for Ru-1222 from SQUID magnetometry and (scaled) Ru XMCD data at 5 K (see text). Lower inset: raw XMCD data at 5 K for $\pm 0$ and $\pm 4\text{T}$ fields. Upper inset: SQUID data for SRO and Ru-1222 samples at 5 K. (b) Main panel: SQUID and (scaled) XMCD data for Ru-1222 at 4 T. Inset: SQUID data for Ru-1222 and SRO at 4T.

Figure 2

(Color online) Crystal structure of Ru-1222 (a) and ${\text{SrRuO}}_3$ (b).

Figure 3

(Color online) Main panel: Magnitude (large symbols) and real part (small symbols) of complex Fourier transform of XAFS data, together with their respective fits (lines), for Ru-1222 at $T=20\mathrm{K}$. Inset: Magnitude of complex Fourier transform of XAFS data for Ru-1222 and ${\text{SrRuO}}_3$.