Magnetic Properties and Mössbauer spectroscopy of NdFe_1-xMn_xO₃

The effect of particle reduction to nanoscale size and substitution of Mn³⁺ ions for Fe³⁺ ions on the crystal structure, lattice dynamics, Mössbauer spectra and magnetic properties in NdFe_1-xMn_xO₃ compounds have been studied. X-ray powder diffraction and Raman spectroscopy revealed that the Jahn-Teller distortion of lattice dominates for samples with x > 0.4. The average particle size of NdFeO₃ nanoparticles (NAP) increases with annealing at 600°C from about 15 nm to 25 nm. The presence of superparamagnetic particles was indicated by Mössbauer measurements in NdFeO₃ NAP system. Sextets in NdFe_1-xMn_xO₃ Mössbauer spectra can be modelled with several local environments of Fe³⁺ induced by substitution. The reduction of dimensionality and the substitution induce a decrease of the Néel temperature T_N1 from 691 K to 544 K for NAP or to 356 K for x = 0.4, however the temperature of spin reorientation T_SR increases with substitution. The saturated magnetization obtained at 1.9 K increases and ferromagnetic component is removed below T_SR with the substitution