Anti-phase boundaries pinned abnormal positive magnetoresistance in Mg doped nanocrystalline zinc spinel ferrite

Two series of Ni and Mg substituted Zn1−xMxFe2O4 (M = Ni, Mg) nanocrystals with different concentration were fabricated by thermal decomposition of EDTA precursor complexes at 600 °C. By changing the doping ions from Ni to Mg, magnetoresistance (MR) changes from negative to positive. The appearance of positive MR in Mg doped ferrite nanocrystals can be mainly attributed to the asymmetric magnetic scattering enhancement of carriers through antiferromagnetic-coupled anti-phase grain boundaries and the suppress of spin-polarized electron tunneling by doping.