Interfacial properties of ${\mathrm{LaMnO}}_3/{\mathrm{LaNiO}}_3$ superlattices grown along (001) and (111) orientations

We have employed x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) at the Ni and Mn $L_{3,2}$ edges in ${\mathrm{LaMnO}}_3/{\mathrm{LaNiO}}_3$ superlattices grown along (001) and (111) orientations. Our results show a significant XMCD signal and thus the presence of magnetic moments localized on both Ni and Mn, which are ferromagnetically coupled to each other. X-ray absorption experiments reveal a charge transfer between Ni and Mn which is larger for (111) than for (001) superlattices. These results are compared to theoretical predictions for such superlattices.

Figure 1

XAS measured at (a) La $M_4$ (846 eV), Ni $L_3$ (849 eV), and Ni $L_2$ (866 eV) edges and (b) only the Ni $L_2$ edge region. Spectra are vertically offset for better visualization.

Figure 2

XAS measured at Mn $L_{3,2}$ edges. The vertical line marks the position of the XAS maxima. Spectra are vertically offset to allow better visualization.

Figure 3

XAS measured at the Ni $L_2$ edge for the SLs (black line). Red lines are fits with a linear combination of the spectra measured for ${\mathrm{NdNiO}}_3$ and NiO. Spectra are vertically offset for better visualization.

Figure 4

XMCD spectra at (a) Ni and (b) Mn $L$ edges measured at 0.5 T and 2 K. The XMCD data are scaled to the XAS spectra shown in Figs. 1 and 2. Spectra are vertically offset to allow better visualization.

Figure 5

(a) Mn and Ni magnetic moments as a function of applied magnetic field for the three SLs. The total magnetization value for Mn and the rescaled Ni magnetization by the ${\mathrm{Ni}}^{2+}$ character (from Table 2) have been divided by $3.45{\mu }_B$ and $1.4{\mu }_B$, respectively. The lines are guides to the eyes. (b) Mn and Ni magnetization curves measured for 5/5 (111) SL after zero-field cooling.

Figure 6

Temperature dependence of the Ni and Mn magnetization obtained from the XMCD signals. Measured under applied field of 75 mT after field cooling at 0.5 T. The XMCD result is compared to the SQUID magnetometry measured in the same sample under similar conditions.