Antiferromagnetic metallic state as proved by magnetotransport in epitaxially stabilized perovskite ${\mathrm{PbRuO}}_3$

Perovskite ${\mathrm{PbRuO}}_3$, which has been synthesized only in bulk polycrystalline form under high pressure, is an orthorhombic Pbnm at room temperature, exhibiting structural phase transition to Imma at around 90 K. This structural transition is accompanied with an orbital ordering and antiferromagnetic spin fluctuation. Here, we report the fabrication of single crystalline perovskite ${\mathrm{PbRuO}}_3$ thin films on various substrates. Magnetotransport measurements reveal that the films have metallic electronic ground state without any clear electronic transitions reported in previous literature. Evidenced by a shift of transition temperature, suppression of magnetic spin fluctuation due to epitaxial strain is implicated. Nonlinear Hall effect is also observed with indiscernible hysteresis, plausibly originating from antiferromagnetic spins, yet multiband effect cannot be completely ruled out.

Figure 1

Growth phase diagram of ${\mathrm{PbRuO}}_3$ thin films. Depending on the growth temperature ($T{}_{\mathrm{sub}}$) and oxygen partial pressure ($P_{{\mathrm{O}}_2}$), the diagram classifies following five regions. (A) both Pb and Ru are evaporated. (B) Ru evaporates as volatile ${\mathrm{RuO}}_3$ and only ${\mathrm{PbO}}_x$ remains. (C) Pb evaporates as volatile PbO and only ${\mathrm{RuO}}_2$ remains. (D) Both Ru and Pb are in amorphous phase. (E) Coexistence region of stable ${\mathrm{Pb}}_2{\mathrm{Ru}}_2{\mathrm{O}}_{6.5}$ and metastable ${\mathrm{PbRuO}}_3$ phases.

Figure 2

(a) X-ray diffraction (XRD) $2\theta -\omega$ scans and (b) magnified data around the (002) (pseudocubic setting) peak of ${\mathrm{PbRuO}}_3$ films on different substrates. The peaks of substrates and ${\mathrm{PbRuO}}_3$ films are denoted by stars and triangles, respectively. (c) Reciprocal space maps (RSM) for ${\mathrm{PbRuO}}_3$ films around (103) peak of LSAT and STO substrates, and around (332) peak of DSO and GSO substrates. ${\mathrm{PbRuO}}_3$ films peaks are denoted by triangles. (d) Out-of-plane lattice constant ($a_{\mathrm{op}}$) for ${\mathrm{PbRuO}}_3$ films on different substrates. The dashed red lines represent the pseudocubic lattice constants for bulk ${\mathrm{PbRuO}}_3$. The blue line represents the strained $a_{\mathrm{op}}$ of ${\mathrm{PbRuO}}_3$ films estimated from a Young's modulus of 0.41.

Figure 3

(a) Device structure for magnetotransport measurements. (b) Temperature dependence of longitudinal resistivity ${\rho }_{xx}$ and (c) its temperature derivative for ${\mathrm{PbRuO}}_3$ films grown on the different substrates. The bulk data are from Ref. [13]. The triangle indicates the transition temperature of the bulk sample.

Figure 4

(a) Magnetic field dependence of the magnetoresistance ratio (MRR) of ${\mathrm{PbRuO}}_3$ films grown on the different substrates. The data are shifted vertically by 0.2% for clarity. (b) Temperature dependence of MRR values at $+9 \text{T}$.

Figure 5

Magnetic field ($B$) dependence of (top panels) ${\rho }_{xx}$ and (bottom panels) ${\rho }_{\mathrm{H}}$ at 2 K for ${\mathrm{PbRuO}}_3$ films grown on the different substrates. Magnetic field derivative is also shown in right axis of each panel. The triangles and the dotted lines indicate the peak position of $\mathrm{d}{\rho }_{\mathrm{xx}}/\mathrm{d}\mathit{B}$. The solid red lines in the bottom panels are fitted curves using the two-carrier model. Deduced density and mobility of majority ($n_1,{\mu }_1$) and minority ($n_2,{\mu }_2$) carriers are indicated.