Comment on “Nodeless pairing state in single-crystal<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>YBa</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Cu</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math>”

In a recent article, Harshman et al. [Phys. Rev. B 69, 174505 (2004)] claim that our $\ensuremath{\mu}\mathrm{SR}$ measurements [Phys. Rev. Lett. 83, 4156 (1999)] of the effective in-plane magnetic penetration depth ${\ensuremath{\lambda}}_{ab}(T,H)$ in high-quality single crystals of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.95}$ are dominated by flux pinning effects, and hence are inconsistent with $d$-wave superconductivity. The purpose of this Comment is to point out that the phenomenological $s$-wave pinning model applied by Harshman et al. to ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ is invaild. The model does not account for the finite size of the vortex cores or the field-induced vortex-lattice transformation, and hence yields inaccurate information on the magnetic penetration depth. We also comment on the criticism of zero-field microwave measurements that show excellent agreement with our $\ensuremath{\mu}\mathrm{SR}$ results for the limiting low-temperature behavior of ${\ensuremath{\lambda}}_{ab}(T)$.

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