Two-population model for anomalous low-temperature magnetism in geometrically frustrated magnets

Strongly geometrically frustrated magnets are unlike other magnetic materials in that the magnetic susceptibility of such materials appears to follow the Curie-Weiss law down to temperatures well below the Weiss temperature. We present an explanation for this anomalous behavior through a phenomenological model of two separate spin populations. The predictions of this model quantitatively describe the experimental data for a wide variety of lattice topologies and levels of disorder. The apparent dual nature of the ground state in some of these materials and the insensitivity of the ground state to disorder also can be understood within this model.