Non-Fermi-liquid behavior in nearly ferromagnetic ${\mathrm{SrIrO}}_3$ single crystals

We report magnetic, electric transport, and calorimetric properties of single-crystal ${\mathrm{SrIrO}}_3$ as a function of temperature $T$ and applied magnetic field $H$. We find that ${\mathrm{SrIrO}}_3$ is a non-Fermi-liquid metal near a ferromagnetic instability, as characterized by the following properties: (1) small saturation moment and no evidence for long-range order down to $1.7\mathrm{K}$, (2) strongly enhanced magnetic susceptibility that diverges as ${\mathrm{T}}^{\gamma }$ at low temperatures with $1∕2<\gamma <1$, depending on the applied field, (3) heat capacity $C(T,H)\sim -T\ln T$ that is readily enhanced in low applied fields, and (4) $T^{3∕2}$ dependence of electrical resistivity over the range $1.7<T<120\mathrm{K}$. The data imply ${\mathrm{SrIrO}}_3$ is a rare example of a stoichiometric oxide compound that exhibits non-Fermi-liquid behavior near a quantum critical point ($T=0$ and ${\mu }_{0}H=0.23\mathrm{T}$).

Figure 1

(Color online) (a) The magnetic susceptibility $\chi$ as a function of temperature at ${\mu }_{0}H=0.5\mathrm{T}$ for $H\Vert \mathbf{c}$ axis $\left({\chi }_c\right)$ and $H\perp \mathbf{c}$ axis $\left({\chi }_{ab}\right)$. $\chi$ for polycrystalline ${\mathrm{IrO}}_2$ is also shown for comparison. Inset: Isothermal magnetization $M$ vs $H$ at $T=1.7\mathrm{K}$. (b) Reciprocal susceptibility ${\chi }_c^{-1}$ and ${\chi }_{ab}^{-1}$ as a function of temperature for ${\mu }_{0}H=0.5\mathrm{T}$. (c) ${\chi }_c^{-1}$ as a function of $T^{1∕2}$ and $T$ (upper scale, for $B=0.8\mathrm{T}$ marked by an arrow). The behavior of ${\chi }_{ab}^{-1}$ is similar and not shown.

Figure 2

(Color online) (a) The specific heat $C$ divided by temperature $C∕T$ vs $\ln T$ for ${\mu }_{0}H=0$, 0.5, 1.1, 3, 5, and $8\mathrm{T}$ and $C$ vs $T^{3∕2}$ (right and upper scales) for ${\mu }_{0}H=8\mathrm{T}$. (b) $\mathrm{\Delta }C∕T$ vs $\ln T$ (see definition of $\mathrm{\Delta }C$ in text) for ${\mu }_{0}H=0$, 1.1, 3, $5\mathrm{T}$. (c) $C∕T$ vs $H$ for some representative temperatures.

Figure 3

(Color online) (a) An $H\text{−}T$ phase diagram generated based on the data in Fig. 2. The dashed line is a guide to the eye. (b) The Wilson ratio $R_W$ as a function of $T$. $R_W$ is estimated based on $\chi$ and $C∕T$ at ${\mu }_{0}H=0.5\mathrm{T}$.

Figure 4

(Color online) (a) The basal plane and $c$-axis resistivity, ${\rho }_{ab}$ and ${\rho }_c$ (right scale) as a function of temperature. (b) ${\rho }_c$ vs $T^{3∕2}$ and $T^2$ (upper scale) for $1.7<T<120\mathrm{K}$ at ${\mu }_{0}H=0\mathrm{T}$. Inset: ${\rho }_c$ vs $T^2$ for $1.7<T<37\mathrm{K}$ at ${\mu }_{0}H=5\mathrm{T}$.