**4. Conclusions**

In summary, this study investigates the effect of Bi3<sup>+</sup> substitution on structural, optical, morphological and magnetic properties of Nd1−<sup>x</sup>BixMnO3 samples. The XRD analysis and Rietveld refinement show the pattern corresponding to the perovskite-type NdMnO3, which crystallizes in the orthorhombic system with main peak at (121) hkl plane with the Pbnm space group. The structural parameter and cell volume of the samples increase as the Bi3<sup>+</sup> content increases. In addition, the average ionic radii of A site, <rA>, increased, hence τ also increased. The FTIR spectra show that active vibrational bands present at 600 cm<sup>−</sup>1–550 cm<sup>−</sup>1, which correspond to the metal oxide Mn–O stretching vibration of perovkite NdMnO3. FESEM images show that the sample is non-spherical and somewhat agglomerated. The samples show a strong AFM behavior at low temperature with decreasing TC due to the Bi substitution. Deviation of temperature dependence of inverse susceptibility curves shows the existence of Griffiths phase in these materials.

**Author Contributions:** Z.M. conceived and designed the experiment; I.S.I. performed the experiments supervised by Z.M. The manuscript was written by N.A.A. and Z.M. with contributions from N.B.M. and A.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was financially supported by the Ministry of Education Malaysia (MOE) and Universiti Teknologi MARA, gran<sup>t</sup> number 600-IRMI/FRGS-RACER 5/3 (042/2019).

**Acknowledgments:** The authors would like to thanks the Faculty of Applied Sciences, Universiti Teknologi MARA for FESEM and FTIR characterization, and Center for Superconducting & Magnetic Novel Oxides of Universiti Teknologi MARA for ACS characterization.

**Conflicts of Interest:** The authors declare no conflict of interest.
