Measurements of the magnetic field penetration depth $\lambda$ in the ternary boride superconductor ${\mathrm{Li}}_2{\mathrm{Pd}}_3\mathrm{B}$ $(T_c\simeq 7.3\mathrm{K})$ have been carried out by means of muon-spin rotation $\left(\mu \mathrm{SR}\right)$. The absolute values of $\lambda$, the Ginzburg-Landau parameter $\kappa$, and the first $H_{c1}$ and second $H_{c2}$ critical fields at $T=0$ obtained from $\mu \mathrm{SR}$ were found to be $\lambda \left(0\right)=252\left(2\right)\mathrm{nm}$, $\kappa \left(0\right)=27\left(1\right)$, ${\mu }_0{H}_{c1}\left(0\right)=9.5\left(1\right)\mathrm{mT}$, and ${\mu }_0{H}_{c2}\left(0\right)=3.66\left(8\right)\mathrm{T}$, respectively. The zero-temperature value of the superconducting gap ${\Delta }_0=1.31\left(3\right)\mathrm{meV}$ was found, corresponding to the ratio $2{\Delta }_0∕k_B{T}_c=4.0\left(1\right)$. At low temperatures $\lambda \left(T\right)$ saturates and becomes constant below $T\simeq 0.2T_c$, in agreement with what is expected for s-wave BCS superconductors. Our results suggest that ${\mathrm{Li}}_2{\mathrm{Pd}}_3\mathrm{B}$ is a s-wave BCS superconductor with only one isotropic energy gap.

• Received 9 January 2006

DOI:https://doi.org/10.1103/PhysRevB.73.214528