Magnetic proximity effect of a topological insulator and a ferromagnet in thin film bilayers of $BiSbTe_3$ and $SrRuO_3$

TL;DR

This study demonstrates the magnetic proximity effect in thin film bilayers of topological insulator $BiSbTe_3$ and ferromagnet $SrRuO_3$, showing suppressed magnetization and altered magnetic hysteresis compared to individual films.

Contribution

It provides experimental evidence of magnetic proximity effects in $BiSbTe_3$/$SrRuO_3$ bilayers through magneto-transport measurements, highlighting changes in magnetization and coercivity.

Findings

50% suppression of magnetization just below $T_c$ in bilayers.

Shift of resistance peak to lower fields indicating magnetic interaction.

Narrowing of coercive peaks by 25-35%, confirming proximity effect.

Abstract

Magnetic proximity effect of a topological insulator in contact with a ferromagnet is reported in thin film bilayers of 15 nm thick $BiSbTe_3$ on either 15 or 40 nm thick $SrRuO_3$ on (100) $SrTiO_3$ wafers. Magneto transport results of the bilayers were compared with those of reference films of 15 nm $BiSbTe_3$ and 15 or 40 nm $SrRuO_3$. Comparison of the temperature coefficient of resistance [(1/R)$\times$dR/dT which is qualitatively proportional to the magnetization] of the bilayer and reference ferromagnetic film normalized above $T_c$, shows a clear suppression in the bilayer by about 50% just below $T_c$, indicating a weaker proximity magnetization in the bilayer. Resistance hysteresis loops versus field at 1.85$\pm$0.05 K in the bilayer and reference films show a clear magnetic proximity effect, where the peak resistance of the bilayer at the coercive field shifts to lower fields by $\sim$30% compared to a hypothetical bilayer of two resistors connected in parallel with no interaction between the layers. Narrowing of the coercive peaks of the bilayers as compared to those of the reference ferromagnetic films by 25-35% was also observed, which represents another signature of the magnetic proximity effect.