Anomalous Hall effect with giant hysteresis loop in ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3|{\mathrm{SrRuO}}_3$ superlattices

We report anomalous Hall effects exhibiting a hysteresis loop as large as about 10 T in a ferromagnetic superlattice comprising ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3$ and ${\mathrm{SrRuO}}_3$ layers. The superlattices grown by pulsed laser deposition exhibit a strong antiferromagnetic interlayer coupling below 110 K, where both ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3$ and ${\mathrm{SrRuO}}_3$ layers show anomalous Hall effects. With increasing magnetic-field strength, the anomalous Hall resistivity in the superlattices changes its sign depending on the magnetization directions of the ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3$ and ${\mathrm{SrRuO}}_3$ layers. As a consequence of competition among the antiferromagnetic interlayer coupling, the Zeeman effect, and magnetic anisotropies, the width of the hysteresis loop in the anomalous Hall resistivity in the superlattices becomes larger than 8 T at 10 K, clearly greater than those observed in ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3$ and ${\mathrm{SrRuO}}_3$ single layer films.

Figure 1

(a) A schematic illustration of the Hall effect measurement for a ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3|{\mathrm{SrRuO}}_3$ superlattice sample. LSMO and SRO denote ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3$ and ${\mathrm{SrRuO}}_3$ layers, respectively. (b) An overview cross-sectional TEM image for a superlattice sample. A magnified view is shown in (c).

Figure 2

(a) Temperature ($T$) dependence of resistivity (${\rho }_{xx}$) for a ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3|{\mathrm{SrRuO}}_3$ superlattice sample. (b) Temperature ($T$) dependence of magnetization ($M$) for a ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3|{\mathrm{SrRuO}}_3$ superlattice sample. The magnetization was measured in a magnetic field of 1 T applied perpendicular to the film plane.

Figure 3

(a) Magnetic-field ($H$) dependence of Hall resistivity (${\rho }_{yx}$) for a ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3|{\mathrm{SrRuO}}_3$ superlattice sample at some temperatures below 300 K. (b) Magnetic-field ($H$) dependence of magnetization ($M$) at 75 K. The dotted lines are just guides for the eyes. Here, the diamagnetic contribution of the ${\mathrm{SrTiO}}_3$ substrate was subtracted from the raw data.

Figure 4

Magnetic-field ($H$) dependence of (a),(c) Hall resistivity (${\rho }_{yx}$) and (b),(d) magnetization ($M$) for a ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3|{\mathrm{SrRuO}}_3$ superlattice sample at 50 K [(a) and (b)] and 10 K [(c) and (d)]. In (b) and (d), the diamagnetic contribution of the ${\mathrm{SrTiO}}_3$ substrate was subtracted from the raw data. As for the magnetization data at 10 K shown in (d), see also Ref. [25].