Low-temperature anomalous spin correlations and Kondo effect in ferromagnetic ${\mathrm{SrRuO}}_3/{\mathrm{LaNiO}}_3/{\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ trilayers

A systematic comparative study of the electronic transport and ferromagnetic resonance of ultrathin trilayers (TLs) of ${\mathrm{SrRuO}}_3/{\mathrm{LaNiO}}_3/{\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$ on (001)- and (111)-oriented ${\mathrm{SrTiO}}_3$ (STO) substrates has been reported. An unusual upturn in resistivity $\rho (T$) at low temperature (so called Kondo-like behavior) accompanied by the negative magnetoresistance has been observed. For temperatures larger than the Kondo temperature $\left(T_{\text{K}}\right)$, $\rho (T$) is in good agreement with the Hamann's impurity resistivity model $\rho (T>T_{\text{K}})\propto {(ln(T/T_{\text{K}}))}^{-2}$ for spin $S=1/2$ and 3/2 for the TLs on (001)-STO and (111)-STO, respectively. At the temperatures $T\gg T_{\text{K}}$, electron-electron $[\rho \left(T\right)\propto T^2]$ contribution dominates over those appearing due to the electron-phonon interaction $[\rho \left(T\right)\propto T^5]$ and 2-Magnon scattering. Using the ferromagnetic resonance near the Curie temperature of ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_3$, we evaluated the contribution of surface anisotropies $\left(K_{\text{s}}\right)$ as well as in-plane volume anisotropies $\left(K_{\nu }\right)$ : $K_{\text{s}}\sim -9.57\times {10}^{-4}$ ($-6.68\times {10}^{-4}$) ${\mathrm{J}/\mathrm{m}}^2$ and $K_{\nu }\sim 4.04\times {10}^5(3.31\times {10}^5$) ${\mathrm{J}/\mathrm{m}}^3$ for the TLs on (001)-STO (TLs on (111)-STO). In addition, the Gilbert damping constant is determined which varies between 0.32 (0.23) and 0.16 (0.19) having spin mixing conductance, ${\mathrm{g}}^{\uparrow \downarrow }=5.2\times {10}^{19}$ ($13.38\times {10}^{19}$) ${\mathrm{m}}^{-2}$ for TLs on (001)-STO ((111)-STO).

Figure 1

Temperature variation of the electrical resistivity $\rho \left(T\right)$ of the trilayer films grown on (001)-oriented STO [(a)–(c)] and (111)-oriented STO [(d)–(f)] in the presence of different magnetic fields ${\mu }_{0}H=0$, 1, and 8 T. At low temperature, upturn in the $\rho$ indicate the presence of Kondo like effect.

Figure 2

Low-temperature resistivity $\rho \left(T\right)$ curves fitted with the relation [Eq. (2)] for the trilayers grown on (001)-oriented STO (a) $\mathrm{TL}{2}_{\left(001\right)}$, (b) $\mathrm{TL}{3}_{\left(001\right)}$, and (c) $\mathrm{TL}{4}_{\left(001\right)}$ and (111)-oriented STO (d) $\mathrm{TL}{2}_{\left(111\right)}$, (e) $\mathrm{TL}{3}_{\left(111\right)}$, and (f) $\mathrm{TL}{4}_{\left(111\right)}$. The black, red and blue scattered symbols represent experimental data points measured at different fields ${\mu }_{0}H=0$, 1, and 8 T, respectively. The solid lines represent best fits to the Eq. (2).

Figure 3

Temperature dependence of electrical resistivity $\rho \left(T\right)$ curves at $T>T_{\text{K}}$ of the trilayers (a) $\mathrm{TL}{2}_{\left(001\right)}$ and (b) $\mathrm{TL}{2}_{\left(111\right)}$ after fitting with the Eq. (3) given in the text. Here the black open circles represent experimental data points, and the red color solid lines represent best fits to the Eq. (3).

Figure 4

Magnetoresistance (MR) $[\mathrm{\Delta }\rho /\rho =(\rho \left(H\right)-\rho \left(0\right))/\rho (0)\times 100)]$ vs field measured at selected temperatures ($T=5$, 50, 100, 150, 200, and 300 K) for the trilayers of different thickness grown on (001)-oriented STO [(a)–(c)] and (111)-oriented STO [(d)–(f)].

Figure 5

Room-temperature ferromagnetic-resonance (FMR) spectra of the trilayer of different thickness grown on (001)-oriented STO [(a)–(d)] and (111)-oriented STO [(e)-(h)].

Figure 6

The effective anisotropy ($K_{\mathrm{eff}}$) vs reciprocal of LSMO thickness ($1/t_{\text{LSMO}}$) for the trilayers on (a) (001)- and (b) (111)-oriented STO substrates. The solid red line represents the linear fit.

Figure 7

LSMO thickness variation of Gilbert damping coefficient $\alpha (1/t_{\text{LSMO}})$ for different thickness of trilayers on (a) (001)- and (b) (111)-oriented STO substrates. The solid red line represents the linear fit.