How thin a spin glass is still a spin glass?

The quasistatic spin-freezing temperature Tf of thin layers of CuMn and AgMn remains nonzero down to thicknesses WSG of 1 and 2 monolayers, respectively. These alloys thus remain spin glasses at such layer thicknesses, in agreement with published evidence of similar behavior for a two-dimensional, short-range, insulating spin glass. For WSG{≤}5 monolayers, we find Tf{∝}WSGᵃ as predicted by Fisher and Huse, with an exponent a=0.8±{}0.1.