Magnetic and transport properties of Cu1.05Cr0.89 Mg0.05O2 and Cu0.96Cr0.95 Mg0.05Mn0.04O2 films

We prepared conductive, polycrystalline or amorphous Cu1.05Cr0.89 Mg0.05O2 films on a-plane sapphire substrates by pulsed laser deposition under different O2 partial pressure and substrate temperature. Hall measurements were performed to study the majority carrier type in these films. Polycrystalline Cu1.05Cr0.89 Mg0.05O2 is n-type conducting at 290 K, while in amorphous Cu1.05Cr0.89 Mg0.05O2 the type of majority charge carriers changes from electrons to holes at around 270 K. Interestingly, the structure has little influence on the magnetic properties of the films. A clear antiferromagnetic to paramagnetic transition was observed in both polycrystalline and amorphous Cu1.05Cr0.89 Mg0.05O2 films at 25 K. Similar electrical properties to Cu1.05Cr0.89 Mg0.05O2 film were observed for Cu0.96Cr0.95 Mg0.05Mn0.04O2 in dependence on the structure, while only paramagnetic without antiferromagnetic ordering was observed down to 5 K. Large negative magnetoresistance of 27% at 20 K was observed at 6 T in amorphous Cu1.05Cr0.89 Mg0.05O2 film.