Coexistence of Superconductivity and Magnetic Order in RuGd$_2$Sr(Cu$_{1-x}$Fe$_x$)$_2$O$_8$ probed by $^{99}$Ru and $^{57}$Fe M\"{o}ssbauer Effects

RuGd$_2$Sr$_2$Cu$_2$O$_8$ develops magnetic order at about 137K and becomes a superconductor at lower temperatures(T$_{SC} \sim$ 40K). T$_{SC}$ decreases with increasing Fe doping in RuGd$_2$Sr$_2$(Cu$_{1-x}$Fe$_x$)$_2$O$_8$ and is zero by $x=.03$. We measure the $^{99}$Ru and $^{57}$Fe M\"{o}ssbauer Effects for x=0, 0.1, 0.2, and 0.3. The $^{57}$Fe M\"{o}ssbauer spectra(MS) show that there are two different Fe sites at 4.2K with very similar hyperfine magnetic fields, $H_{hyper}\sim 48$ T. However $H_{hyper}$ goes to zero at $\sim$half the Fe sites in a temperature range between 30K and 40K in superconducting and non-superconducting samples. There is no significant change in $H_{hyper}$ in the $^{99}$Ru MS in this temperature range. We conclude that the Fe sites whose $H_{hyper}$ does not change are in the magnetically ordered RuO planes. We assume that the Fe's which see the transition between 30K and 40K are in the CuO planes and investigate how this transition arises.