Spin-transfer torque provides an important mechanism for controlling thin films of magnetic material with thicknesses on the nanometer scale, and can significantly effect the orientation of a magnet to cause reversal and switching. I examine the iron garnets, yttrium iron garnet (Y3Fe5O12, YIG) and lutetium iron garnet (Lu3Fe5O12, LuIG), to investigate the interaction of spin-torque on electrically-insulating magnets. This insulating property prevents electrical current from shunting through the iron garnet magnet, which improves the amount of current available to generate spin-torque with the spin-Hall effect in an adjacent heavy metal. I demonstrate that nanometer-scale devices can be fabricated out of ultra-thin YIG and LuIG, and explore their switching behavior. I construct a ferromagnetic resonance measurement system to characterize the YIG and LuIG material and understand their properties. Using this system, I explore the magnetic damping in ultra-thin LuIG, and YIG at low-temperatures to explain the relaxation phenomena that occur in these systems. Overall, this research provides a significant step forward in understanding the properties of thin-films of iron garnet, and the feasibility of using spin-transfer torque on electrically-insulating materials.