Magnetic properties of non-magnetic impurities in geometrically frustrated magnets

Non-magnetic impurities (vacancy defects) are a common type of quenched disorder in geometrically frustrated (GF) magnets and have a dramatic effect on their magnetic properties. Experimentally, vacancy defects in GF magnets have been demonstrated to act as effective spins, ``quasispins’’, in response to an external magnetic field at low temperatures. In this work, we investigate microscopically the magnetic properties and thermodynamics of quasispins in GF magnetic materials. We compute the values of quasispins of vacancy defects and their entropy in the Ising model on common GF lattices. We further use phenomenological arguments to extend our results to Heisenberg models.