Annealing-Induced Magnetic Modulation in Co- and Y-Doped CeO₂: Insights from Experiments and Density Functional Theory

The potential applications of dilute magnetic oxides (DMOs) in magneto-optic and spintronic devices have attracted significant attention, although understanding their magnetic behavior is complex due to complex interactions of intrinsic defects. The present study aims to investigate the effect of different annealing environments on the magnetic properties of polycrystalline transition metal cation (Co and Y)-doped CeO2 DMO with a 5% doping concentration of transition metal (TM). The objective is to investigate the defect interactions within the lattice through a comprehensive investigation involving structural characterizations, magnetic measurements, and first-principle calculations. The results show that the Ar/H2 annealing environment induced more oxygen vacancies than air-annealed samples. Consequently, field-dependent magnetization measurements revealed above-room-temperature ferromagnetism (RTFM) in both undoped and TM-doped CeO2. The ferromagnetic (FM) properties of CeO2 resulted from carrier-trapped vacancy centers facilitating exchange interactions between the spins of magnetic ions. The Langevin field profile indicated that TM-doped CeO2 formed more bound magnetic polarons (BMPs) during annealing in an Ar/H2 environment, which contributed to the enhanced ferromagnetism. Similarly, enhancement in the magnetic properties with increasing oxygen vacancies is observed through first-principle calculations. This suggests the potential for optimizing the magnetic properties of DMOs through controlled annealing processes.