A series of n-type Zn1−xCuxO (x=0.02, 0.06, 0.10, and 0.12) films was prepared using direct current reactive magnetron sputtering. Magnetic measurements indicate that all the films are ferromagnetic at room temperature and the moment per Cu ion decreases with increasing copper concentration and nitrogen doping. The observed magnetic moment was 1.8μB∕Cu for Zn0.98Cu0.02O film and the transition temperature of about 350K decreased to 320K due to nitrogen doping. It can be concluded that itinerant electrons play an important role in ferromagnetism. The resistivity increased with increasing copper concentration and nitrogen doping. The anomalous Hall effect has been found for ferromagnetic materials.

A giant exchange bias field of up to 1170 Oe was observed in the Mn2Ni1.6Sn0.4 Heusler alloy. A reentrant spin glass phase and a ferromagnetic martensitic phase coexist below the blocking temperature as confirmed by dc magnetization and ac susceptibility measurements. Exchange bias in Mn2Ni1.6Sn0.4 is thought to originate from the interface exchange interaction between the reentrant spin glass phase and the ferromagnetic martensitic phase. X-ray diffraction and selected area electron diffraction results demonstrate that excess Mn atoms occupy Ni and Sn sites randomly. In this way, Mn-Mn clusters are formed and constitute the reentrant-spin-glass phase.

Despite low resistivity (~ 1 m cm), metallic electrical transport has not been commonly observed in the inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and degree of spinel inversion on the electrical conduction of NiCo2O4 films.In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (111) and on Al2O3 (001) substrates. Although the optimal growth conditions are similar for the NiCo2O4 (111)/MgAl2O4 (111) and the NiCo2O4 (111)/Al2O3 (001) films, they show metallic and semiconducting electrical transport respectively. Post-growth annealing decreases the resistivity of NiCo2O4 (111)/Al2O3 (001) films, but the annealed films are still semiconducting. While the semiconductivity and the large magnetoresistance in NiCo2O4 (111)/Al2O3 (001) films cannot be accounted for in terms of the non-optimal valence mixing and spinel inversion, the presence of * Corresponding authors. 2 anti-phase boundaries between nano-sized crystallites, generated by the structural mismatch between NiCo2O4 and Al2O3, may explain all the experimental observations in this work. These results reveal nanostructural disorder as another key factor in controlling the electrical transport of NiCo2O4, with potentially large magnetoresistance for spintronics applications.

Understanding the cation distribution and electronic transport properties of half-metallic NiCo2O4 (NCO) films is crucial to advancing their practical applications in optoelectronic materials.