a Department of Physics, Hindusthan College of Engineering and Technology,

Coimbatore, India-641021

b Department of Physics, Government College of Technology, Coimbatore - 641

013, India

c Centre for Materials Science, Karpagam Academy of Higher Education,

Coimbatore, India-641 021

d Department of Physics, Faculty of Arts Science Commerce and Management,

Karpagam Academy of Higher Education, Coimbatore, India-641 021

e Department of Physics, Saveetha Engineering College,Thandalam,Chennai -

602105

NiMnO3, a perovskite oxide, is renowned for its exceptional physical and chemical characteristics, affordability, and non-toxicity. In this work, we investigate how cobalt (Co) doping affects the optical, magnetic, and structural characteristics of NiMnO3 nanoparticles made using the hydrothermal method. Powder X-ray diffraction (XRD), UV- visible spectroscopy, photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM) were used to evaluate the produced NiMnO3, NiMn₀.95Co₀.₀5O3,and NiMn₀.9Co₀.₀O3nanoparticles. XRD analysis confirm the rhombohedral crystal structure with a minor shift in peaks indicating successful doping of Co. UV-Vis spectroscopy revealed a decrease in bandgap with increasing Co concentration, while PL analysis showed a reduction in near band edge and increase in emission intensity, defect level transitions. SEM images highlighted a change in morphology and particle size with higher Co doping. Magnetic studies demonstrated an increase in coercive field with Co content, indicating enhanced magnetic anisotropy and exchange interactions.