Indication for macroscopic quantum tunneling below 10 K in   nanostructures of SrRuO3
  We study magnetization reversal of nanostructures of the itinerant ferromagnet SrRuO3 (Tc~150 K). We find that down to 10 K the magnetization reversal is dominated by thermal activation. From 2 - 10 K, the magnetization reversal becomes independent of temperature, raising the possibility for reversal dominated by macroscopic quantum tunneling (MQT). A 10 K crossover to MQT is consistent with the extremely large anisotropy field (~7 T) of SrRuO3. 
Omer Sinwani, James W. Reiner and Lior Klein
cond-mat.mes-hall cond-mat.str-el