Investigation of structural, magnetic, and electronic properties of Co doped NdMnO3

Polycrystalline NdMn_1-xCo_xO₃ (x = 0.0, 0.3, 0.7) samples were synthesized utilizing the conventional ceramic method. The X - ray diffraction patterns subjected to Rietveld refinement uncover the single-phase orthorhombic crystal structure for all the samples. Temperature-dependent magnetization executed at 0.05 T and 1.0 T reveal the transition from ferromagnetic to paramagnetic phase at Curie temperature T_c (∼ 60–140 K). In all the samples, zero field cooled (ZFC) and field cooled (FC) curves separate at thermo-magnetic irreversibility temperature (T_irr), except in x  = 0.0 sample, at a higher field of 1 T. The ZFC curve displays the cusp showing maximum at temperature T_m. T_m and T_irr shift to lower temperatures with a broad maximum in ZFC as the external field is increased in x  = 0.3 & 0.7 samples indicating ferromagnetic ordering. At a temperature of 10 K, magnetization versus magnetic field (M−H) curves undoubtedly imply the ferromagnetic interactions at low fields up to 3 T, and at fields greater than 3 T a distinctive antiferromagnetic character is evident that is pronounced in x  = 0.7 sample. At T = 150 K, the M−H curve indicates paramagnetic behavior in x  = 0.0 & 0.7 samples; however, in x  = 0.3 sample, a slight non-linearity suggests feeble ferromagnetic interactions at tiny fields typically below 1 T.

The detailed analysis of X-ray absorption spectroscopy (XAS) spectra at L_3,2- edges of manganese (Mn) and cobalt (Co) ions along with O K-edge reveal that Mn exhibits mixed valent states i.e. Mn ³⁺/Mn⁴⁺ and Co shows high spin Co²⁺ and high/low spin Co³⁺ state. These results are confirmed using charge transfer multiplet calculations done at L_3,2 edges of Mn and Co ions. X-ray photoelectron spectroscopy (XPS) conducted at Mn2p, Co2p, and O1s −edges serves to reinforce and validate the XAS results.