Nonmagnetic element induced novel ferromagnetism in CoFeTiAl quaternary Heusler alloy

The CoFeTiAl1-xSix (x = 3.125%) compound with Heusler structure was studied by theory and experiment. An unexpected diluted magnetism is found with a Curie temperature of 100 K. The calculated electronic structures show that the spin-splitting of DOS only occurs in p-like the states achieved by p-d hybridization near Fermi level and leads to the ferromagnetism when the Si content is lower than 6%. The magnetic moment is not localized on any atom but distributed in a region with the doped Si atom as the center. An anomalous hall effect is observed, which confirms the ferromagnetism in Si-doped CoFeTiAl alloy. A magnetoresistance of 0.375% for CoFeTiAl1-xSix is observed at 2 K.