Antiferromagnetism in Fe and Os doped URu$_2$Si$_2$ studied by $\mu$SR

URu$_2$Si$_2$ is a material that has been studied extensively for almost three decades in an effort to characterize its unusual ``hidden order'' state. One common method used to study this compound is to perturb the ground state by doping the Ru site with various metals. Such doping usually causes the transition temperature to drop, and the hidden order state to transition into an antiferromagnetic state. In contrast to this common behavior, the isoelectronic dopings Fe and Os cause a substantial increase in the transition temperature over a wide range of dopings. However, the magnetic states of these dopings have not been well characterized, with only a small number of studies on polycrystalline samples reported in the literature. In this talk, we present an investigation of the magnetic properties of single crystal samples of URu$_{2-x}$Fe$_x$Si$_2$ and URu$_{2-x}$Os$_x$Si$_2$. Our $\mu$SR results demonstrate that both of these dopings show an antiferromagnetic ground state between $x = 0.1$ and $x = 0.4$ that evolves with increasing temperature into the paramagnetic state by a second order transition.