Correlation between the Effective Amounts of Elements in TbFeCo Thin Films and Their Magnetic Properties

Abstract

In this study, TbFeCo thin films were prepared using DC-magnetron sputtering technique utilizing a conventional batch-type sputtering machine. The properties such as magnetic hysteresis loops and magneto-optical properties of the obtained films were measured. Furthermore, we precisely evaluated the “effective” amounts of elements, i.e., the amounts of constituents released by oxidation, in TbFeCo thin films. We also attempted to control the amounts of effective elements by changing the pre-sputtering condition before film preparation. This is because the pre-sputtering process greatly affected the effective amounts of elements in the prepared TbFeCo thin films, such that the magnetic properties were drastically different from sample to sample by altering the pre-sputtering condition. Insufficient pre-sputtering led to a relatively high oxygen content in the films in comparison with those prepared with sufficient pre-sputtering. Outstanding perpendicular magnetic anisotropy in the out-of-plane direction was observed in a film prepared after 60 min of pre-sputtering, which exhibited a coercivity (H_c⊥) value of 6.4 kOe from magnetic hysteresis measurements and 8.2 kOe from magneto-optical polar Kerr hysteresis measurements at an incident light of wavelength 700 nm. The saturation value of the polar Kerr rotation angle (θ_K) of this film was approximately 0.3°, which is comparable to the theoretically optimized value. Therefore, we demonstrated that high-quality TbFeCo films can be obtained with high reproducibility by using a simple batch-type sputtering machine and that there is a strong correlation between effective amounts of elements in TbFeCo thin films and their magnetic properties.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 82 (2018) 140–146.

Fig. 8 Comparisons of the magneto-optical properties of TbFeCo films after 3 and 60 min of pre-sputtering. Polar Kerr hysteresis loops measured at (a) the film surface and (b) the substrate side at an incident light wavelength of 700 nm. Changes in θ_r values as a function of incident light wavelength for measurements at (c) the film surface and (d) the substrate side.