Magneto-optic and magnetic properties of praseodymium substituted garnets

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Abstract
On PrxY3−x Fe5O12 substituted garnets magnetic magnetization and Faraday rotation (φF) have been measured in the 4.2–300 K temperature range with magnetic field applied parallel to the ‖111‖ direction. The wavelength varies from 1 to 1.3 μm and three Pr3+ concentrations 1.10, 0.70, and 0.35 were studied. At 4.2 K, the spontaneous magnetic moment attributed to one Pr3 ion is deduced from the Néel model to be (1.55±0.15) μB as previously found in polycrystalline samples. At 1.15 μm wavelength the contribution of the Pr sublattice to φF is determined assuming the contribution of the Fe3+ ions equal to the YIG experiemental data. φF induced by one Pr3+ ion is found identical in the three ferrites of various concentrations for T≳90 K. Below this temperature, discrepencies of about 15% between the Pr3+ contributions to φF were evaluated. Characteristic values are obtained: −(475±25) deg cm−1 at 300 K, −(700±50) deg cm−1 at 90 K, −(1800±200) deg cm−1 at 9 K. Such a behavior which shows the one ion model to be valid is completed by the study of the θF dispersions in the 1.05–1.3 μm wavelength range at 300 and 77 K, respectively. By comparison between diamagnetic and paramagnetic type Faraday contribution the high rotation of the Pr3+ ions is attributed to a newly observed paramagnetic transition close to 5500 Å (18.180 cm−1).