Uniaxial magnetocrystalline anisotropy in $\mathrm{Ca}\mathrm{Ru}{\mathrm{O}}_3$

$\mathrm{Ca}\mathrm{Ru}{\mathrm{O}}_3$ is a paramagnetic metal and since its low temperature resistivity is described by $\rho ={\rho }_0+A{T}^{\gamma }$ with $\gamma \sim 1.5$, it is also considered a non-Fermi liquid (NFL) metal. We have performed extensive magnetoresistance and Hall effect measurements of untwinned epitaxial films of $\mathrm{Ca}\mathrm{Ru}{\mathrm{O}}_3$. These measurements reveal that $\mathrm{Ca}\mathrm{Ru}{\mathrm{O}}_3$ exhibits uniaxial magnetocrystalline anisotropy. In addition, the low-temperature NFL behavior is most effectively suppressed when a magnetic field is applied along the easy axis, suggesting that critical spin fluctuations, possibly due to proximity of a quantum critical phase transition, are related to the NFL behavior.

Figure 1

Rescaled resistivity of four patterns as a function of temperature. In two patterns the current is along [100] while in the other two the current is along (010). Inset: A sketch of the patterned film. The crystallographic directions 1 (easy axis) and 2 (hard axis) are at 45° out of the plane of the film.

Figure 2

MR data at 2, 5, and $30\mathrm{K}$ for $\mathbf{H}=3\mathrm{T}$ as a function of the angle $\theta$ between $\mathbf{H}$ and the normal to the sample in the (100) plane. (a) Pattern with current path along the (010) direction. (b) Pattern with current path along the (100) direction.

Figure 3

MR data for current path along the (100) direction at 2 and $5\mathrm{K}$ for $\mathbf{H}=3\mathrm{T}$ as a function of the angle $\theta$ between $\mathbf{H}$ and the normal to the sample in the (010) plane.

Figure 4

HE data as a function of the angle $\theta$ between $\mathbf{H}$ and the normal to the sample in the (100) plane with curves that are fit of $\cos (\theta +\phi )$ (a) and in the (010) plane with curves that are fit of $\cos \theta$ (b).

Figure 5

$R_0+R_s{\chi }_1$ and $R_0+R_s{\chi }_2$ as a function of temperature.

Figure 6

$\gamma$ as a function of the magnetic field, $\mathbf{H}$, applied along three different orientations. Easy axis (EA) (011) is the direction of the easy axis of magnetization.

Figure 7

MR data as a function of temperature at $\mathbf{H}=4\mathrm{T}$. EA (011) is the direction of the easy axis of magnetization.