Tailoring the bandgap and magnetic properties by bismuth substitution in neodymium chromite

The intrinsic distortions present in rare-earth orthochromites $$(\hbox {RCrO}₃)$$ observed from lanthanum to lutetium (in R-site) can influence the magnetic properties like Neel transition and weak ferromagnetic coupling. A nonmagnetic cation with similar ionic radius would be a suitable candidate to engineer the inherent distortions of particular orthochromite. In this study, bismuth $$(\hbox {Bi}³⁺)$$ with a $$6s²$$ lone pair was chosen to substitute in neodymium $$(\hbox {Nd}³⁺)$$ site of $$\hbox {NdCrO}₃$$ (NCO) to tailor the intrinsic structural distortions. The variation of optical absorption edge evidently suggests that Bi $$(6{s}²)$$ substituted in the magnetic rare-earth $$\hbox {Nd}³⁺$$ influences the Cr–O overlap integral. The interaction of Bi cation with oxygen bonds influences the structural distortions through Cr–O polyhedral, which are evident from Raman scattering studies. The observed structural and magnetic properties of similar ionic radius of $$\hbox {Bi}³⁺$$ in $$\hbox {Nd}³⁺$$ reveal that intrinsic structural distortions are interrelated to enhanced weak ferromagnetic component and change in Neel and spin reorientation temperatures in our compounds. In addition, a reduction in the optical bandgap of NCO from 3.1 to 2.6 eV was observed.