Quantum phase transition in Fe/Cr multilayers tuned by a magnetic field

We report on the spin dependent electron transport near the transition from a ferromagnetic into an antiferromagnetic (AFM) state. We find that in the [Fe/Cr](10) multilayers the resistivity rho(s) associated with the AFM sca ttering at 4 < T < 100 K varies as rho(s)(T) = rho(s)(0) - AT(alpha) with 0 .5 < alpha(H) less than or equal to 2. As T --> 0 K, rho(s) saturates excep t for a magnetic field region near H = H-s(o), which tunes the Arn? transit ion down to 0 K. For temperatures upwards from 20 mK with H = H-s(o) a cros sover between two linear in T dependences of rho(s) is observed, indicating a possible transition from the critical quantum to the thermal spin fluctu ations around 2-3 K.