“One-pot” growth method for rare-earth transition metal TbFeCo alloy films with desirable magnetic properties

Significance 

Rare-earth transition metal alloys, particularly ternary TbFeCo alloy films, have been extensively researched for various potential practical applications in high-density spintronic devices. Typically, TbFeCo comprises of the rare-earth Tb and transition metal FeCo materials that exhibit paramagnetic and ferromagnetic effects at room temperature, respectively. TbFeCo alloys also undergo magnetic compensation because the Tb and FeCo sublattices are antiferromagnetically coupled to allow cancelation of the opposite moments of the sublattices when the film losses magnetic properties. Generally, magnetic field materials with perpendicular magnetic anisotropy(PMA) exhibit the advantages of high thermal stability, high-density, and scalability desired for various applications. Recently, TbFeCo alloy films with anisotropy and adjustable perpendicular switching fields have been identified as potential candidates for developing low-current driven spintronic devices. Consequently, it has been reported that the perpendicular magnetic anisotropy and magnetic properties of the sputtered TbFeCo films can be enhanced by varying various parameters, including the composition, film thickness, buffer material, and post-growth annealing. Nevertheless, such modifications require an efficient and cost-effective method for fabricating TbFeCo alloys with desirable properties.

To this note, a research group from the East China University of Technology (ECUT), led by Professor Ke Wang, investigated the modification of the perpendicular magnetic properties of ferrimagnetic TbFeCo alloys fabricated by sputtering a composite target method. This research was highly motivated by the promising results of their previous work, where they noted that the magnetic properties of the films could be adjusted appropriately. In this approach, extraordinary Hall effect measurements were used to study the perpendicular magnetic properties of the TbFeCo films. The work is currently published in the Journal of Materials Science.

The research team found that an increase in either gas flow rate or the sputtering power shifted the film composition from FeCo-rich to Tb-rich. It also changed the orientation of the magnetic easy axis from the in-plane to out-of-plane directions. Also, increasing the Tb-to-FeCo ratio of the film alloy enhanced the magnetic properties of the alloys, particularly the coercivity property. Furthermore, it was worth noting that tilting the magnetic easy axis of the TbFeCo alloy films at a specific angle for specific applications could be achieved by selecting the most suitable sputtering conditions for fabrication purposes. “This simple “one-pot” method allows us to easily and quickly grow TbFeCo alloy films with preferred magnetic properties, ” Prof. Ke Wang comments.

In summary, this is the first study to report the manipulation of the magnetic properties of the TbFeCo film alloy materials using the gas flow rate parameter. Results showed that an appropriate combination of the sputtering power and flow rate during the film growth could result in the fabrication of TbFeCo films with improved perpendicular magnetic properties such as coercivity. The efficient approach for modification of the perpendicular magnetic anisotropy of the sputtered TbFeCo films during growth, as demonstrated in the study, represented a significant milestone in the research of rare-earth transition-metal alloys films. In a statement to Advances in Engineering, Professor Ke Wang- the School Head, said their study will advance designing TbFeCo-based spintronic devices with low power consumption.

"One-pot" growth method for rare-earth transition metal TbFeCo alloy films with desirable magnetic properties - Advances in Engineering

About the author

Prof. Ke Wang received his PhD degree in Microelectronics and Solid State Electronics in 2000 from Huazhong University of Science and Technology (HUST). His research expertise lies in the areas of magnetic/optical/electronic thin films and devices, particularly for information storage. He previously received Alexander von Humboldt (AvH) research award to carry out his work in RWTH-Aachen. Currently, he is heading the School of Mechanical and Electronic Engineering, East China University of Technology (ECUT). Prof. Wang serves as Editorial Board Member for over ten scientific journals, and as Chair and/or Keynote speaker for several conferences. He has published more than 70 peer reviewed papers and holds several patents.

Reference

Wang, K., Tang, Y., Xiao, X., Xu, Z., & Liu, J. (2021). Fabrication of TbFeCo alloy films with tunable perpendicular coercivity evaluated by extraordinary Hall effect measurementsJournal of Materials Science, 56(5), 4013-4021.

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