Magnetic Properties of epitaxial $\text{Re}/{\text{Co}}_{1-x}{\text{Au}}_x/\text{Pt}$ heterostructures

Abstract

We investigate epitaxial $\text{Co}(20\text{A˚})$ and ${\text{Co}}_{1-x}{\text{Au}}_x(20\text{A˚})$ alloy thin-films surrounded by asymmetric heavy metals layers of $\text{Re}(10\text{A˚})$ as a buffer and $\text{Pt}(30\text{A˚})$ as a cap to study the magnetic anisotropy, interfacial Dzyaloshinskii-Moriya interaction (iDMI) and damping. The increase of Au from 0% to 25% in the ${\text{Co}}_{1-x}{\text{Au}}_x$ alloy generates the spin-reorientation transition of around 13% of Au. The increase in Au concentration provides a significant decrease in saturation magnetization from 1690 kA/m to 982 kA/m measured for Co and ${\text{Co}}_{75}{\text{Au}}_{25}$, respectively. The effective anisotropy constant ${\text{K}}_{eff}$ is elevated up to 0.33 ${\text{MJ/m}}^3$ by changing the Au content. Further, our investigations of the magnetization dynamics have confirmed that the overall effective damping constant rises with the Au concentration which can be attributed to the spin pumping effect. The spin pumping leads to the highest value of effective spin mixing conductance $g^{(\uparrow \downarrow )}\approx 2.91\times 10^{18}{\text{m}}^{-2}$ in the ${\text{Co}}_{90}{\text{Au}}_{10}(20\text{A˚})$ system, while the lowest value of $g^{(\uparrow \downarrow )}\approx 2.25\times 10^{18}{\text{m}}^{-2}$ is found for the $\text{Co}(20\text{A˚})$ system. Additionally, we have investigated the iDMI strength, and the amplitude of iDMI decreases with increasing Au concentration. The highest surface iDMI constant value equal to 2.62 pJ/m is observed for Co.