Origin of the high-temperature ferromagnetism in Co-doped PbPdO2 semiconductors: A theoretical and experimental study

High-temperature ferromagnetism has always been a classic and interesting subject, especially in spin gapless semiconductor PbPdO2 with exotic properties. Here, a combination of theoretical and experimental studies was employed to clarify the origin of high Tc. First, based on first-principles calculations, electronic band structures of PbPd0.875Co0.125O2 at different Co substitution positions were studied. Our results indicate that Co atoms tend to form an antiferromagnetic ground state due to the Co–O–Co (180°) indirect exchange effect, while ferromagnetism is favored in Co-doped PbPdO2 when a unique molecular field effect induced band crossover and p–d coupling occurs. It is revealed that metallic or semiconductor properties have an important connection with ferromagnetism or antiferromagnetism. Subsequently, a Monte Carlo simulation was carried out based on the first-principles results to predict the ferromagnetism of PbPd0.875Co0.125O2. Finally, the moment-magnetic field and moment-temperature curves were also measured for PbPd0.875Co0.125O2 samples, which was found well consistent with the theoretical findings. The ground state of PbPd0.875Co0.125O2 was confirmed to be ferromagnetic. Our results well explain the origin of high-temperature ferromagnetism in diluted magnetic semiconductors and provide new approaches for the design of future high Tc spintronic devices.