Optical and magneto-optical properties of NdTbFeCo thin films

Abstract

Three series of NdxTbyFe1−x−y−zCoz films have been fabricated for their potential application in magneto-optical recording: (i) x=0–0.20, Tb was adjusted so that the coercivity at room temperature was 5–10 kOe; (ii) x+y=0.28–0.32 with x in the range of 0 to 0.25; and (iii) x+y=0.21–0.23 with x in the range of 0 to 0.17. These films have been characterized both optically and magneto-optically by Kerr hysteresis trace, variable angle of incidence ellipsometry, and normal angle of incidence Kerr spectroscopy. From these measurements, the optical constants (n and k), magneto-optical constants (Q1 and Q2), and maximum possible figure of merit (FOM) have been determined at wavelengths of 405, 546, and 633 nm. Results demonstrate that the magneto-optical behavior of NdTbFeCo films is sensitive to the concentration of both Nd and Tb in the film. For samples in the series (i), the addition of Nd into TbFeCo alloys was shown not to enhance their magneto-optic behavior at the short wavelengths. For samples in the series (ii) and (iii), the substitution of Nd improves the magneto-optical performance greatly at blue light. But at red and green wavelengths it has little effect on the magneto-optical properties in samples in the series (iii) or degrades in samples in the series (ii). The maximum enhancement in the FOM is about 25% at x∼10% for blue light.