Quantum vortex melting in Nb/CuMn multilayers

We have measured the electrical resistance R vs temperature T in different perpendicular magnetic fields on Nb/CuMn multilayers. The samples had constant Nb layer thickness (∼230 Å) and CuMn layer thicknesses in the range 4–50 Å. Below the zero-field superconducting critical temperature ${\mathit{T}}_{\mathit{c}}$, the (lnR vs 1/T) curves showed a sharp change in the slope at magnetic-field-dependent temperatures ${\mathit{T}}^{\mathrm{*}}$(H). The ${\mathit{T}}^{\mathrm{*}}$ vs H curves are consistent with vortex-lattice melting, mainly due to quantum fluctuations. © 1996 The American Physical Society.