Effect of Co doping at the Ho– and Fe–sites on the structural, optical and magnetic properties of HoFeO3 nanoparticles synthesized by co–precipitation method

This study investigates the effects of Co doping at the Ho– and Fe–sites in HoFeO3 (HoFeO3, Ho0.9Co0.1FeO3, and HoFe0.9Co0.1O3) on the elemental, structural, thermal, optical, and magnetic properties of nanosized perovskite–like HoFeO3. Thermogravimetric analysis (TGA) revealed that Co doping at the Ho–site resulted in a greater reduction in mass upon calcination compared to doping at the Fe–site. Co doping at the Ho–site led to oxygen deficiency, while the sample with Co doping at the Fe–site and the undoped HoFeO3 sample exhibited an oxygen redundant in the perovskite structure. Additionally, Co doping at the Ho–site reduced the average crystallite size and unit cell volume compared to the other samples. The Ho0.9Co0.1FeO3 sample exhibited increased visible light absorption, with a narrower band gap (Eg = 1.94 eV) than that of the undoped HoFeO3 (Eg = 2.13 eV) and HoFe0.9Co0.1O3 (Eg = 1.98 eV) samples. Both the Co–doped samples showed hard ferromagnetism. Specifically, the coercivity (Hc = 1042.13 Oe) and remanence (Mr = 1.34·100 emu·g−1) of the Ho0.9Co0.1FeO3 sample were 8 and 46 times higher, respectively, than those of the HoFe0.9Co0.1O3 sample (Hc = 130.02 Oe, Mr = 2.92·10−2 emu·g−1).