- Effect of Neodymium and Transition Metals Co-doped on Structural, Optical and Magnetic Properties of BiFeO 3 Materials. - All samples exhibit a weak ferromagnetic behavior at room temperature with the enhancement of the magnetization in Nd and TM co-doped samples.. - Due to the simultaneous coexistence of ferroelectric, ferromagnetic and ferroeleastic phase, multiferroics materials recently are interested in many research groups all over the world. - direction of the cubic perovskite-like lattice [3, 5, 6]. - In order to solve these problems, a chemical modification doping rare earth or transition metals ions into A- or B-sites of the perovskite BFO is strongly recommended [9, 10]. - The magnetoelectric effect in these materials was assigned to the coupling between ferroelectric order resulting from electron lone pair of A-site Bi 3+ ions and the ferromagnetic order resulting from the substitution of cation Fe 3+ into B-site [27].. - In this study, neodymium and transition metals co-doped BFO samples were synthesized by sol- gel method. - The influence of neodymium and transition metals co-doped on the microstructures, surface morphology, magnetic and optical properties of materials were investigated.. - Vibrating sample magnetometer was used to measure magnetic properties of the samples. - 1a shows XRD patterns of the BFO, BNFO, BNFNO and BNFCO samples. - Impurities phases are not detected in BFO and BNFO samples but they are found in BNFNO and BNFCO samples. - For co- doped samples, these peaks shift closer together and tend to merge into a single peak. - These changes in XRD patterns indicate that the lattice parameters of the BNFO, BNFNO and BNFCO samples are altered by doping especially in co-doping samples. - This change could be attributed to the difference of ion radius between the host lattice ions Bi3+ and Fe3+ to replacing ions Nd3+ and Ni2+ (Co2+) respectively [27].. - XRD patterns of the BFO, BNFO, BNFNO and BNFCO powders.. - Raman spectra of BFO, BNFNO and BNFCO powders at room temperature.. - The structural transformation of BNFNO and BNFCO materials are also observed in Raman spectra. - 2 shows the Raman spectra of BFO, BNFNO, and BNFCO samples. - It is interesting to note that the E-3 modes at 293 cm -1 is detected in BNFNO sample which is not observed in the BFO and BNFCO samples. - Co-doped samples (BNFNO and BNFCO) exhibit the shift of three Raman modes A 1 -1, A 1 -2 and A 1 -3 to higher frequency. - Moreover, the shift of E-3 and E-8 modes to higher frequency reveals the increase of local lattice distortion and the formation of oxygen vacancy due to substitution of the Ni, Co dopant at the B site [7, 31]. - The appearance of a prominent additional band around ∼ 1000 – 1350 cm −1 in co-doped samples can be assigned to the two-phonons Raman scattering in BFO labeled as 2A 4 , 2E 8 and 2E 9 [30]. - The strong contribution of these two-phonon bands to the total Raman spectrum has been attributed to a resonant enhancement with the intrinsic absorption edge in BFO [32, 33].. - (a)-(d) SEM images of the BFO, BNFO, BNFNO and BNFCO materials, respectively.. - The particle size generally decreases in doped and co-doped samples comparing to un-doped BFO sample. - 4a shows UV–Vis absorption spectrum of BFO, BNFO, BNFNO and BNFCO samples (insert figure is the plots of ( α h ν ) 2 versus (h ν ) for the BFO sample). - The band gap values obtained by Wood- Tauc method for BFO, BNFO, BNFNO and BNFCO samples are 2.03, 2.00, 1.97, and 1.85 eV, respectively (in Fig. - The appearance of second absorbance at 700 nm can be assigned to the transition of electron from t 2g bands to e g bands of Fe 3+. - The slight decrease of optical band gap in doped and co-doped samples can be explained by the appearance of Nd impurity band in the energy band gap. - 4a also exhibit a weak absorption peak at 750 nm for doped and co-doped BFO samples which can be assigned to electron transitions from the ground state 4 I 9/2 to the excited levels ( 4 F 7/2 + 4 S 3/2 ) of Nd 3+ ion [36].. - (a) UV–Vis absorption spectrum of the BFO, BNFO, BNFNO and BNFCO samples. - The insert shows the plot of ( α hv) 2 as a function of photon energy of the BFO. - (b) optical band gap of the samples, respectively.. - Magnetic-field dependence of the magnetization for BFO, BNFO, BNFNO and BNFCO materials.. - 5 presents the magnetic hysteresis (M ‐ H) loops of the BFO, BNFO, BNFNO and BNFCO samples under the maximum field of 10 kOe at room temperature. - The magnetizations sharply increase in co-doped BFO samples comparing to un-doped and Nd-doped BFO samples. - The calculated saturation magnetization values of the BFO, BNFO, BNFNO and BNFCO samples are 0.155, 0.211, 2.262 and 1.808 emu/g, respectively. - [7] reported that the enhanced magnetic moment of co-doped samples can be assigned to the transition of magnetic structure from incommensurate cycloidal spiral spin structure to G-type collinear antiferromagnetic structure.. - The doped, co-doped and un-doped BiFeO 3 materials were prepared by sol–gel method. - The replacement of Nd into A-sites and Co (Ni) into B-site were observed through the shift of XRD peaks resulting the change of lattice parameters and the shift of Raman peaks which related to the vibration of replacing sites. - Weak ferromagnetism was observed in all samples with the sharply increase of saturation magnetization values H C in co-doped BFO samples comparing to un-doped BFO and Nd-doped BFO samples.. - Mazumder and A.Sen, J