Finite-size effects: hydrogen in Fe/V(001) superlattices.

We investigate the effect of finite size on phase boundaries of hydride formation in ultrathin metallic films, using Fe/V(001) superlattices as a model system. The critical temperature is determined to scale linearly with the inverse thickness of the V layers. The decrease of the ordering temperature with decreasing layer thickness arises from the missing H neighbors at the interfaces, analogous to observed finite-size effects in magnetic layers and nanosized ice crystals.