Domain Behavior in Some Transparent Magnetic Oxides

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Abstract
Magnetic domains were observed by means of the Faraday effect, and by the Bitter technique in a number of compounds having the spinel, magnetoplumbite, and perovskite‐like structures. The latter compounds are orthorhombic and have the general formula MFeO3 where M is Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. Domain boundaries in these compounds move for fields less than one oersted, and after saturation, crystals as large as (∼0.2×0.2×0.1 in.) remain single domains. Fields of 2500 oersteds are required to reverse the magnetization in the single domain crystals. Reversal occurs by nucleation and growth of a reverse domain. This is evident from the unusual torque curves. The fact that domain walls occur and move in such weak fields in these compounds indicate that the slight or parasitic magnetization is a uniform body property of the crystals. The parasitic magnetization of these compounds was determined from torque measurements. These crystals are well suited for light modulators because a uniaxial anisotropy holds the magnetization vectors normal to the large surfaces of thin flat crystals and weak fields produce changes in magnetization. Absorption coefficients were measured for some compounds for radiation having wavelengths from 0.6 μ to 13 μ. Thin sections were found to be transparent to light at the red end of the visible spectrum. The Faraday rotation was measured for Li0.5Fe2.5O4, MgFe2O4, YFeO3, and PbFe11Al1O19.