Paramagnetic resonance line shapes and magnetic parameters of polycrystalline substances

A closed-form expression for the paramagnetic resonance line shape of a polycrystalline substance is derived on the assumption of axial symmetry, a crystallite line shape that is Lorentzian, random orientation of the crystallites, and a spin Hamiltonian that consists of Zeeman, dipolar and exchange terms only. Some representative line shapes are evaluated from this expression and are compared with previous, approximate calculations. An iterative procedure for the derivation of magnetic parameters from polycrystalline spectra is described. As an example of this procedure the magnetic parameters of polycrystalline potassium perchromate are derived. © 1962 The American Physical Society.