Competing magnetic fluctuations in ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$ probed by Ti doping

We report the effect of nonmagnetic ${\mathrm{Ti}}^{4+}$ impurities on the electronic and magnetic properties of ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$. Small amounts of Ti suppress the characteristic peak in magnetic susceptibility near $16\mathrm{K}$ and result in a sharp upturn in specific heat. The metamagnetic quantum phase transition and related anomalous features are quickly smeared out by small amounts of Ti. These results provide strong evidence for the existence of competing magnetic fluctuations in the ground state of ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$. Ti doping suppresses the low-temperature antiferromagnetic interactions that arise from Fermi surface nesting, leaving the system in a state dominated by ferromagnetic fluctuations.

Figure 1

(Color online) Temperature dependence of the uniform susceptibility $\chi =M∕H$ of Ti-doped ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$ for (a) in-plane and (b) out-of-plane fields, taken using an excitation field of ${\mu }_{0}H=0.3\mathrm{T}$.

Figure 2

The specific heat divided by temperature for Ti-doped ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$ at low temperatures.

Figure 3

(a) Magnetization versus field and (b) resistance (normalized to its $0\mathrm{T}$ value) versus field for the ${\mathrm{Sr}}_3{\left({\mathrm{Ru}}_{1-x}{\mathrm{Ti}}_x\right)}_2{\mathrm{O}}_7$ system. Magnetization is taken at $2\mathrm{K}$ and resistance is measured at $0.3\mathrm{K}$.

Figure 4

(a) The temperature dependence of the resistivity for several Ti doping levels, normalized to the resistivity at $10\mathrm{K}$. (b) Resistivity (normalized to its $0.3\mathrm{K}$ value) plotted versus $T^2$ for metallic doped samples. The data of the $x=0.5\%$ sample are not shown here, since they nearly overlap with those of the pure sample. This is likely due to Ti inhomogeneity. Inset: resistivity of the 3.0%-doped sample versus $T^2$, under a range of applied fields, ${\mu }_{0}H=5.0$, 4.0, 5.5, 3.0, 6.0, 0.0, 7.0, 8.0, and $9.0\mathrm{T}$, from top to bottom. $I\Vert H\Vert ab$.