The magneto-optical Faraday effect is determined by the electric dipole and magnetic dipole transitions in a transparent magnetic material. At the same time, the inverse Faraday effect is still described by an expression that includes only electric dipole transitions. The magnetic dipole contribution to the inverse Faraday effect is considered theoretically, and the dependence of the inverse Faraday effect on the wavelength in the near-infrared range (where the magnetic dipole contribution becomes significant) is obtained by the example of a ferrite–garnet film. It is shown that, although both contributions to the inverse Faraday effect always take place for homogeneous films, only the magnetic-dipole inverse Faraday effect manifests itself for films with a periodic nanostructure upon excitation by a TE waveguide mode, which may be useful for its experimental observation.

Terahertz (THz) electromagnetic pulses offer a promising route for the ultrafast manipulation of magnetization in ferromagnetic materials. While previous studies have demonstrated the excitation of spin dynamics using linearly polarized THz fields, the role of circular polarization and the effects of rapidly oscillating, time-dependent field profiles remained insufficiently understood. We have developed a unified theoretical framework for describing the excitation of spin precession via Zeeman interaction in magnetic materials by high frequency pulses of arbitrary polarization with temporal Gaussian profile. In the regime of long pulses (at least several oscillations are within the pulse duration), a circularly polarized magnetic field acts as an effective rectified magnetic field along the pulse propagation, while linear polarized pulses excite no free precession. In the regime of short pulses (less than one oscillation is within the pulse duration), pulses of any polarization, including linear one can excite free spin precession. There is an optimal pulse duration which maximizes amplitude of the spin precession. It depends on magnetic parameters of the sample and the external magnetic field, as well as on the carrier frequency of the pulse and its amplitude. These findings bridge key gaps in the understanding of THz-induced spin dynamics and provide insights into the design of light-controlled magnetization schemes using tailored electromagnetic pulses.

Магнитооптический эффект Фарадея определяется электро-дипольными и магнито-дипольными переходами в прозрачном магнитном материале. В то же время обратный эффект Фарадея до сих пор описывали выражением, которое учитывает только электродипольные переходы. В работе теоретически рассмотрен магнитодипольный вклад в обратный эффект Фарадея и на примере пленки ферритаграната получена зависимость обратного эффекта Фарадея от длины волны в ближнем инфракрасном диапазоне, где магнитодипольный вклад становится существенным. Показано, что хотя для однородных пленок всегда присутствуют оба вклада в обратный эффект Фарадея, для пленок с периодической наноструктурой при возбуждении ТЕ-волноводной моды проявляется только магнитодипольный обратный эффект Фарадея, что может помочь его обнаружить экспериментально.