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In this paper, we present a derivation of the nonlinear susceptibility tensors for a two-sublattice uniaxial antiferromagnet up to the third-order effects within the standard definition by which the rf magnetization m is defined as a power series expansion in the rf fields h with the susceptibility tensors as the coefficients. The starting point is the standard set of torque equations of motion for this problem. A complete set of tensor elements is derived for the case of a single-frequency input wave. Within a circular polarization frame (pnz) expressions are given for the first-order susceptibility, second-harmonic generation, optical rectification, third-harmonic generation and intensity-dependent susceptibility. Some of the coefficients with representative resonance features in the far infrared are illustrated graphically and we conclude with a brief discussion of the implications of the resonance features arising from the calculations and their potential applications.

We derive the equations of motion from which nonlinear field- and frequency-dependent magnetic susceptibilities defined by M = + + may be calculated for a Heisenberg ferromagnet. Explicit expressions are given, in the circular polarization frame, for the second- and third-order effects that arise for a single-frequency input wave, namely second-harmonic generation, optical rectification, third-harmonic generation and intensity-dependent susceptibility. Illustrative graphs are presented for a few of the coefficients and the paper concludes with a brief discussion of the implications for multistability of a magnetic Fabry-P?rot resonator.

The transmission of electromagnetic radiation at normal incidence through a magnetic film is considered for film thickness L small enough to require the inclusion of exchange effects arising from the wave-number component . We apply the continuum form of the dynamical equations with parametrized spin boundary conditions including pinned and unpinned spins as special cases. For applied field normal to the interfaces (Faraday geometry) the propagating modes are circularly polarized but because of the exchange there are two modes, say optical and spin, in each polarization. Equations for the transmission are given in a general form that allows for partial mirrors at the interfaces and applies to a film on a substrate as well as a free-standing film. Computed transmission spectra show that spin-wave fringes are unlikely to be observable for ferromagnets but can be significant in antiferromagnets. Some discussion is given of the implications for the characterization of antiferromagnetic film systems by means of far-infrared spectroscopy.

We discuss the transmission of electromagnetic radiation through a Fabry - Perot resonator in the microwave or far-infrared frequency ranges where the magneto-optic properties are governed by a gyromagnetic permeability tensor. We restrict our attention to normally incident radiation but consider both Faraday (magnetic field normal to plate) and Voigt (field parallel to plate) geometries for ferromagnets and antiferromagnets. The effect of partially reflecting mirrors is included. It is shown that provided one uses the polarization eigenmodes, circular for Faraday geometry and plane for Voigt geometry, the transmission and reflection can be expressed by general formulae in terms of single-interface reflection and transmission coefficients. The resonator can be regarded as a magnetic-field tunable polarizer and it is shown how inclusion of mirrors sharpens the properties.