Amorphous magnetic alloys possess unique magnetic properties ranging from very low coercivity to uniaxial magnetic hardness. These materials offer vast opportunities for alloying and their synthesis does not involve epitaxial growth, making them particularly desirable for energy conversion and nanoelectronic applications. Amorphous rare-earth-transition-metal (a-RE-TM) thin films with perpendicular magnetic anisotropy (PMA) are studied for high-density, low-power, and ultrafast non-volatile memory applications. a-RE-TM are ferrimagnets composing antiferromagnetically coupled RE and TM sublattices. The magnetization of the sublattices compensates each other at the compensation temperature (Tcomp). These amorphous ferrimagnetic films exhibit large coercivity fields of several Tesla. Novel magnetic states can be obtained by appropriately configuring the nanoscale structure of the thin film. The mechanisms involved are verified by micromagnetic and atomistic simulations. The ability to control these new properties in amorphous films without the need for epitaxial growth opens a new avenue for enhancing the functionalities of spin-based materials.