  This paper presents an overview of Unidirectional Loop Metamaterial (ULM)
structures and applications. Mimicking electron spin precession in ferrites
using loops with unidirectional loads (typically transistors), the ULM exhibits
all the fundamental properties of ferrite materials, and represents the only
existing magnetless ferrimagnetic medium. We present here an extended
explanation of ULM physics and unified description of its component and system
applications.
