Glassy ferromagnetism in Al-doped 4H-SiC: AlSi–VCVC complexes

The recent observed glassy ferromagnetism in Al-doped 4H  -SiC is investigated using first principles calculations. We find that the formation energy of VCVC is significantly reduced by Al atoms doped in SiC. The AlSi–VCVC complex induces a half-filled narrow a1a1 level in the band gap and contributes a net local moment of 1 μBμB. The exchange parameter J can be either positive or negative along different directions. Both the strong anisotropy of J   and the correlation effects of the a1a1 level can lead to a glassy ferromagnetism in Al-doped 4H-SiC.