Theory of ion pairs coupled by exchange interaction

The theory of the properties and magnetic behaviour of a system of two coupled spins is given. The coupling is of the most general linear exchange type, including asymmetric and anisotropic contributions. The system shows many properties of a weak ferromagnet when the interaction is predominantly antiferromagnetic. The energy level scheme, static and dynamic susceptibility. magnetic resonance, and the behaviour in the classical limit of large spins are studied in detail. © 1966.