Recently, rare-earth transition metal alloys have attracted significant attention of researchers owing to their excellent physical and chemical properties thus a great potential in supporting numerous applications. In particular, TbFeCo alloy films have found applications in several areas including logic memories and ultra-fast magnetic switching, attributed to their good perpendicular magnetic anisotropy. Presently, several techniques for fabricating ternary alloy films with good perpendicular magnetic anisotropy have been proposed. For instance, it can be achieved around the compensation composition point due to the cancelation of the coupled rare-earth and transition metals.
Unfortunately, the factors leading to perpendicular magnetic anisotropy in rare-earth metal transition TbFeCo alloys have not been fully investigated. To this note, researchers have proposed numerous models to clarify the origin of perpendicular anisotropy especially in amorphous alloy films and also as a means of enhancing their properties. Regardless of the remarkable progress, the effects of thickness and substrate on the magnetic properties of thin films are still missing.
To this end, East China University of Technology scientists led by Professor Ke Wang investigated the effects of thin film thickness and substrate on the perpendicular magnetic properties of TbFeCo thin films. Fundamentally, the ultra-thin TbFeCo films were fabricated using a radio frequency sputtering method. Specifically, the authors hoped to develop an efficient method for optimizing the magnetic properties of thin rear-earth transition alloys so as to promote their applications. Their research work is currently published in the journal, Surface and Coatings Technology.
In brief, the research team started by characterizing the perpendicular films using extraordinary Hall effect measurement technique. Based on the polarity of the Hall effect, magnetic spins of the ferrimagnetic alloys were examined so as to get more insights on the magnetic properties of the TbFeCo alloys. Furthermore, they investigated the transition from the FeCo-dominant to Tb-dominant TbFeCo film configuration as well as the relationship of the film thickness, extraordinary Hall effect polarity, and substrate to the magnetic properties.
The authors observed that the increase in the film thickness resulted in a corresponding increase in the PMA strength. Consequently, low saturation magnetization and large coercivity resulted in a critical compensation thickness of approximately 14nm. This further led to polarity change which was attributed to the transition from the FeCo-dominant toTb-dominant configuration. On the other hand, the authors noted that the substrate used for deposition significantly influenced the magnetic properties of the films.
In summary, East China University of Technology researchers successfully investigated the influence of substrate and thickness on the magnetic properties of the thin TbFeCo films. In general, the magnetic properties depended greatly on the substrate and thickness of the films. The study is important because it resulted in an efficient new method for optimizing the magnetic properties of TbFeCo alloys films which will not only enhance their properties but also increase their application in several fields.
“The concept of critical thickness is equivalent to compensation composition in ferrimagnetic materials, which provides a powerful and handy way to tailor the magnetic properties of ultra-thin rare-earth transition metal films. This concept can be used in magnetospintronic device fabrications to meet a wide range of applications ” said Professor Ke Wang, the lead author in a statement to Advances in Engineering.
Wang, K., Dong, S., & Xu, Z. (2019). Thickness and substrate effects on the perpendicular magnetic properties of ultra-thin TbFeCo films. Surface and Coatings Technology, 359, 296-299.Go To Surface and Coatings Technology