Figure 1

(a) The reflection high energy electron diffraction (RHEED) intensity oscillation observed during the deposition of a noncentrosymmetric ${\mathrm{S}\mathrm{r}\mathrm{T}\mathrm{i}\mathrm{O}}_3/{\mathrm{L}\mathrm{a}\mathrm{A}\mathrm{l}\mathrm{O}}_3/{\mathrm{L}\mathrm{a}}_{0.6}{\mathrm{S}\mathrm{r}}_{0.4}{\mathrm{M}\mathrm{n}\mathrm{O}}_3$ (STO/LAO/LSMO) superlattice on a ${\mathrm{S}\mathrm{r}\mathrm{T}\mathrm{i}\mathrm{O}}_3$ (001) substrate. By counting the RHEED oscillation, the thicknesses of the constituent layers were controlled on an atomic scale, i.e., with the accuracy of the unit cell height (0.4 nm). The thickness of the LSMO, LAO, and STO are 10, 2, and 3 unit cells (u.c.), respectively. (b) Second harmonic (SH) intensity of some perovskite superlattices composed of magnetic ${\mathrm{L}\mathrm{a}}_{0.6}{\mathrm{S}\mathrm{r}}_{0.4}{\mathrm{M}\mathrm{n}\mathrm{O}}_3$ (LSMO), and nonmagnetic ${\mathrm{S}\mathrm{r}\mathrm{T}\mathrm{i}\mathrm{O}}_3$ (STO) and/or ${\mathrm{L}\mathrm{a}\mathrm{A}\mathrm{l}\mathrm{O}}_3$ (LAO) thin layers; noncentrosymmetric STO[3 u.c.]/LAO[2 u.c.]/LSMO[10 u.c.] tricolor superlattice, centrosymmetric LAO[2 u.c.]/LSMO[10 u.c.], and STO[5 u.c.]/LSMO[10 u.c.] bicolor superlattices. The photon energy of fundamental light is 1.55 eV. Angle of incidence is $45°$. The inset shows the experimental configuration. (c) Schematic structure of three kinds of perovskite superlattices.Reuse & Permissions

Figure 2

Polarization dependence of the SH light of noncentrosymmetric STO/LAO/LSMO tricolor superlattice at 10 K. Angles of incidence ($\Theta$) are (a) $26°$ and (b) $13°$, respectively. An external magnetic field $B$ was applied along the $x$ direction. [See Fig. 1b for the experimental setup.] Solid circles: $+0.35\mathrm{T}$; open circles: $-0.35\mathrm{T}$. The inset shows the dependence of nonlinear Kerr rotation $\varphi$ on the angle of incidence $\Theta$. A solid line is a fitted curve with the relation that $\tan \varphi \propto 1/\sin \Theta$.Reuse & Permissions

Figure 3

Polarization dependence of the SH light of noncentrosymmetric STO/LAO/LSMO tricolor superlattice at (a) 10 K, (b) 100 K, and (c) 300 K. Angle of incidence ($\Theta$) is $26°$. Solid circles: $+0.35\mathrm{T}$; open circles: $-0.35\mathrm{T}$. (d) Temperature dependence of Kerr rotation angle $\varphi$ (solid circles), normalized magnetization of noncentrosymmetric STO/LAO/LSMO tricolor superlattice (solid line), and bulk LSMO (a dashed line) [for the bulk LSMO, temperature on the abscissa is normalized so that its transition temperature (370 K) may coincide with that of the tricolor superlattice]. The dotted line is a guide for the eyes. Open circles show linear combination of the normalized magnetization of bulk LSMO and the nonlinear Kerr rotation angle $\varphi$. The magnetization was probed by a superconducting quantum interference device (SQUID) magnetometer in a magnetic field of 0.5 T applied parallel to the film plane, i.e., the same direction as in the MSHG experiment. (e) The temperature dependence of $p$-polarized SH intensity.Reuse & Permissions