Critical thickness for itinerant ferromagnetism in ultrathin films of   SrRuO$_3$
  Ultrathin films of the itinerant ferromagnet SrRuO$_3$ were studied using transport and magnto-optic polar Kerr effect. We find that below 4 monolayers the films become insulating and their magnetic character changes as they loose their simple ferromagnetic behavior. We observe a strong reduction in the magnetic moment which for 3 monolayers and below lies in the plane of the film. Exchange-bias behavior is observed below the critical thickness, and may point to induced antiferromagnetism in contact with ferromagnetic regions. 
Jing Xia, W. Siemons, G. Koster, M.R. Beasley, and A. Kapitulnik