Effects of perpendicular interlayer coupling strength on canting angles of TbCo-sublattice magnetization

We investigate the perpendicular interlayer coupling between Co/Pt multilayers and Co/TbCo bilayers through the Ru spacer with various thickness. The canting angles of the Tb and Co moments are determined by x-ray magnetic circular dichroism. We observe that the interlayer exchange coupling oscillates and aligns Co and Tb moments in opposite directions. As a consequence, the canting angles of the Tb and Co moments correlate with the strength of the interlayer coupling and agree with our theoretical calculations as well. The opposite alignment on the TbCo-sublattice magnetizations from the interlayer coupling cannot be viewed as an effective magnetic field and thus is unique with potential applications for spintronics devices.

Figure 1

(Color online) XMCD spectra of $\text{Tb}{M}_{4,5}$-edge and $\text{Co}{L}_{2,3}$-edge with $P$ and $A$ incidences on the ${\left[\text{Co}/\text{Pt}\right]}_5/\text{Co}/\text{Ru}\left(t_{\text{Ru}}\right)/\text{Co}/\text{TbCo}$ samples with the spacer thickness $t_{\text{Ru}}=1.25\text{nm}$. The experimental setup is shown schematically here with the definitions for the canting angles.

Figure 2

(Color online) The canting angles of the Co (blue diamonds) and the Tb (orange dots) moments in TbCo layer at different spacer thickness. The solid lines are the numerical solutions for the canting angles from the theoretical model discussed.

Figure 3

(Color online) Hysteresis loops of the ${\left[\text{Co}/\text{Pt}\right]}_5/\text{Co}/\text{Ru}\left(t_{\text{Ru}}\right)/\text{Co}/\text{TbCo}$ samples with (a) $t_{\text{Ru}}=1\text{nm}$ and (b) $t_{\text{Ru}}=2\text{nm}$.

Figure 4

(Color online) The strength of interlayer coupling $\left|J\right|$ (purple diamonds) and the relative angle (blue dots) versus the thickness of the Ru spacer in ${\left[\text{Co}/\text{Pt}\right]}_5/\text{Co}/\text{Ru}/\text{Co}/\text{TbCo}$ samples. The pink and blue shaded colors denote the AF and the $F$ regimes of the overall interlayer coupling. The solid and dashed lines are theoretical fits to the experimental data.