<P> Magnetochemistry is concerned with the magnetic properties of chemical compounds . Magnetic properties arise from the spin and orbital angular momentum of the electrons contained in a compound . Compounds are diamagnetic when they contain no unpaired electrons . Molecular compounds that contain one or more unpaired electrons are paramagnetic . The magnitude of the paramagnetism is expressed as an effective magnetic moment, μ . For first - row transition metals the magnitude of μ is, to a first approximation, a simple function of the number of unpaired electrons, the spin - only formula . In general, spin - orbit coupling causes μ to deviate from the spin - only formula . For the heavier transition metals, lanthanides and actinides, spin - orbit coupling cannot be ignored . Exchange interaction can occur in clusters and infinite lattices, resulting in ferromagnetism, antiferromagnetism or ferrimagnetism depending on the relative orientations of the individual spins . </P> <P> The primary measurement in magnetochemistry is magnetic susceptibility . This measures the strength of interaction on placing the substance in a magnetic field . The volume magnetic susceptibility, represented by the symbol χ v (\ displaystyle \ chi _ (v)) is defined by the relationship </P>

Quenching of orbital angular momentum in transition metal complexes