Prof.  Ke  Wang
East China University of Technology,  China

Title: Ultrathin heavy rare-earth transition metal alloy films and multilayers investigated by extraordinary Hall effect (EHE) measurements

Abstract:

Keywords: Heavy rare-earth transition metal alloy films; Extraordinary Hall effect (EHE); Ultrathin films; Perpendicular exchange bias.

Abstract. Ultrathin heavy rare-earth transition metal (HRE-TM) alloy films have been attracting considerable attention for their current applications in spintronics, ultrafast magnetism and magnonics. In the HRE-TM alloys, the HRE and TM sublattice magnetizations are antiferromagnetically coupled. There may exit a compensation point, where the moments of the HRE and TM sublattices cancel out each other  and the net magnetization is zero. Extraordinary Hall effect (EHE) technique is particularly useful in characterizing HRE-TM alloy films around compensation composition, where the strong perpendicular anisotropy appears and the net magnetization is low.

In this talk, ultrathin TbFeCo and GdFeCo alloy films are investigated by EHE measurements. The sign of the extraordinary Hall resistance is observed to change from positive for TM-rich films to negative for RE-rich films and a high extraordinary Hall coefficient is obtained. For the bilayers a large perpendicular exchange bias is found at room temperature. Our results show HRE-TM alloy films and multilayers are promising for designing perpendicular magnetoelectronic devices.

This work was supported by the National Natural Science Foundation of China (Grants No. 52261042).

References

[1]     K. Wang, et al. Extraordinary Hall effect of sputtered amorphous ferrimagnetic GdFeCo alloy films, Materials Today Communications 35, 10602,2023.

[2]     K. Wang, et al. Tuning perpendicular magnetic properties of sputtered rare-earth transition metal GdFeCo alloy films, Journal of Superconductivity and Novel Magnetism 34(9), 2455-2461, 2021

[3]     K. Wang, et al. Fabrication of TbFeCo alloy films with tunable perpendicular coercivity evaluated by extraordinary Hall effect measurements, Journal of Materials Science 56, 4013–4021, 2021

[4]     K. Wang, et al. Thickness and substrate effects on the perpendicular magnetic properties of ultra-thin TbFeCo films, Surface and Coatings Technology 359, 296-299, 2019

Biography:

Prof. Ke Wang obtained his BS and Ph.D degrees in microelectronics and solid state electronics from Huazhong University of Science and Technology. Currently, Prof. Wang is heading the School of Mechanical and Electronic Engineering in the East China University of Technology. Previously, he received Alexander von Humboldt (AvH) research award to carry out his work in RWTH-Aachen. Prof. Wang serves as Editorial Board Member for over ten scientific journals and as the Editor for publishing several international conference proceedings. He has published more than 80 peer reviewed papers and holds several patents. His expertise covers magnetic/optical/electronic thin films and nanostructured devices.