Kerr Rotation Angle versus Gobalt Sublattice Magnetic Moment in RE-Co Sputtered Films

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Abstract
Kerr rotation angles, θ K, at 780 nm of an optical wavelength, λ, are measured at room temperature for RE(Gd, Tb, Dy, Nd)-Co sputtered films in a wide range of RE content. The absolute rotation angle |θ K| decreases linearly with an increase in RE content. This compositional dependence of θ K is analyzed using the mean field theory. From this analysis, it is found that the absolute value of θ K is proportional to the Co sublattice magnetic moment, M Co, with the coefficient of about 3.3 × 10-4 deg·cm3 / emu at δ = 780 nm. This linear relation indicates that θ K of RE-Co films arises mainly from the Co moment, M Co, at this wavelength. Furthermore, the Kerr rotations of Co-Ti, Co-Zr and Co-Cr sputtered films are measured. They are also proportional to the saturation magnetization, M s, with the coefficients of values nearly equal to those of RE-Co films.