Effects of finite size on critical phenomena: The resistivity anomaly in Ni films

The electrical resistivity of Ni films ranging in thickness from 250 to 24000 {} has been measured precisely near the Curie point. A shift in the temperature of the point where dρdT is maximum is observed which goes as n^-λ, where n is the number of atomic layers and the shift exponent λ is found to be 1.01±{}0.10. The amplitude of the dρdT anomaly is observed to go as ln(n). Moreover, the shape of the anomaly is observed to broaden as one decreases n. Attempts to scale the data for all films along the lines suggested by Fisher and Barber are only partially successful and gave a rounding exponent θ of about 0.6. This value of θ is not considered to be reliable.