Enhancement of ferromagnetism by nickel doping in the 112 cobaltite   EuBaCo2O5.50
  The study of the ordered oxygen deficient perovskite EuBaCo2-xNixO5.50 shows that the doping of cobalt sites by nickel induces a strong ferromagnetic component at low temperature in the antiferromagnetic matrix of EuBaCo2O5.50. This system exhibits indeed phase separation, i.e. consists of ferromagnetic domains embedded in the antiferromagnetic matrix of EuBaCo2O5.50. Besides, a magnetic transition is observed for the first time at 40K in the undoped and nickel doped phases, which can be attributed to the ferromagnetic ordering of the Eu3+ moments below this temperature. Moreover sharp ultra magnetization multisteps are observed below 5K, characteristic of motion of domain walls in a strong pinning system and very different from any metamagnetic transition. 
B. Raveau, Ch. Simon, V. Caignaert, V. Pralong and F.X. Lefevre