We study the interplay of superconductivity, ferromagnetism, and the Kondo effect in a single system, using vertical geometry and planar magnetic tunnel junction devices, in which a thin CoFe layer is inserted in the middle of the MgO layer, forming a quantum dot like system. It is shown that the Kondo resonance peak at the zero bias coexists with a sharp Bardeen-Cooper-Schrieffer gap on double tunnel junctions, Al/MgO/CoFe nanodot/MgO/Al. It is also found that the competition between superconductivity and the Kondo effect is tunable with magnetic fields and the temperature. The coexistence of Kondo screening and superconductivity survives long range magnetic order in CoFe nanodots with a spin polarization of 0.2; however, it disappears when the CoFe layer becomes a continuous film with a spin polarization of 0.5. The competition between SC and the Kondo effect in the presence of magnetic ordering opens exciting possibilities to control information in nanomagnets.
Bibliographical noteFunding Information:
This research was partly supported by the National Science Centre, Poland, Grant Nos. 2015/17/B/ST3/02799 and 2020/36/C/ ST3/00539. M.-S.C. was supported by the National Research Foundation of Korea (Grant Nos. 2018R1A4A1024157 and 2017R1E1A1A03070681) and the Ministry of Education of Korea (BK21 Four).
© 2021 Author(s).
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)