Synthesis, characterization and magnetic properties of LaFeO3 nanoparticles by EDTA assisted Sol-Gel method

Introduction

Perovskite-type oxides with the general formula ABO₃ have garnered considerable attention due to their versatile functional properties and wide-ranging applications in catalysis, gas sensing, magnetic devices, and fuel cells [1][2][3][4][5][6][7] . Among them, lanthanum orthoferrite (LaFeO₃) stands out as a prominent member of the perovskite family, exhibiting excellent chemical stability, narrow bandgap, and antiferromagnetic behavior [8,9] . Lanthanum orthoferrite (LaFeO₃) crystallizes in a distorted perovskite structure, which deviates from the ideal cubic perovskite form due to the size mismatch between the A-site (La³⁺) and B-site (Fe³⁺) cations. This structural distortion results in an orthorhombic unit cell, where the three lattice parameters are unequal (a ≠ b ≠ c) but the interaxial angles remain at 90°, a characteristic of orthorhombic symmetry [10] . LaFeO₃ specifically belongs to the Pbnm space group, which is a common subgroup of perovskite structures associated with tilting of the BO₆ octahedra and reduced symmetry [11] . Experimental studies, particularly those involving X-ray diffraction and Rietveld refinement, have determined the lattice constants of LaFeO₃ to be approximately a = 5.557 Å, b = 5.565 Å, and c = 7.854 Å, indicative of the slight distortion from cubic symmetry [12] . The perovskite framework is composed of corner-sharing FeO₆ octahedra, where each Fe³⁺ ion is surrounded by six O²⁻ ions in an octahedral geometry. These octahedra are interconnected in a three-dimensional network, with the larger La³⁺ ions occupying the interstitial A-sites [8,13] . Magnetic characterization through neutron diffraction has revealed that LaFeO₃ exhibits a canted G-type antiferromagnetic (AFM) ordering. In this magnetic arrangement, each Fe³⁺ ion is magnetically coupled with six nearest-neighbor Fe³⁺ ions in an antiparallel (Antiferromagnetic) fashion, forming a G-type pattern [11] . However, due to a slight misalignment or "canting" of spins attributed to the antisymmetric Dzyaloshinskii-Moriya interaction a weak ferromagnetic component is also present [14,15] . The material undergoes antiferromagnetic ordering at a relatively high Néel temperature (Tₙ) of around 740 K, highlighting its thermal stability and potential for high-temperature magnetic applications [13,16] . The structural stability of the ABO₃ perovskite lattice is predominantly governed by the Goldschmidt tolerance factor (t), which provides insight into the geometric compatibility of the A and B-site cations within the oxygen framework. In the case of LaFeO₃, the tolerance factor is found to be less than unity (t < 1), indicating a mismatch in ionic radii that causes a deviation from the ideal cubic symmetry. This deviation favors the formation of a lower-symmetry orthorhombic structure, characterized by tilted and distorted FeO₆ octahedra. As a consequence of this structural distortion, the Fe-O-Fe bond angle is reduced from the ideal 180°, resulting in bent connections between adjacent FeO₆ octahedra. This tilting significantly affects the electronic bandwidth and magnetic exchange interactions, thereby influencing the overall physical properties of the material [17] . The properties of LaFeO₃ can be strategically tailored through several modification techniques. One common approach involves reducing the particle size, which increases the surface area and can enhance properties such as catalytic activity and magnetic behavior [18] . Another effective strategy is cationic substitution at the A-site (La³⁺) or B-site (Fe³⁺), which can alter the structural, electronic, and magnetic characteristics of the material [19][20][21][22] . At the nanoscale, LaFeO₃ exhibits behaviors that are markedly different from its bulk counterpart due to a higher surface-to-volume ratio and quantum confinement effects. These nanoscale features enable fine-tuning of its functional properties, making nanostructured LaFeO₃ a promising candidate for advanced applications in catalysis, sensing, and spintronic devices [2325] . In response to the increasing demand for nanomaterials with controlled size, morphology, and enhanced functionality, attention has shifted toward more refined wet chemical synthesis techniques. These methods offer significant advantages, including lower processing temperatures, improved phase purity, and greater control over particle uniformity and distribution [26] . Recent advancements in solution-based synthesis routes have further enabled the fabrication of ultrafine, stoichiometrically precise, and highly homogeneous mixedmetal oxide nanoparticles, paving the way for scalable and reproducible production tailored for advanced technological applications [27] . A wide range of wet chemical synthesis techniques have been explored for the fabrication of nanosized LaFeO₃, offering improved control over morphology and composition. These methods include hydrothermal synthesis [3,28] , co-precipitation [29,30] , autocombustion [31,32] , sol-gel processing [2,33,34] , microwaveassisted synthesis [1,35,36] , sonochemical methods [37,38] , polymerizable complex (Pechini) routes [39,40] , microemulsion techniques [41,42] and the sucrose-driven auto-combustion [43] . Although many of these strategies have successfully produced nearly phase-pure LaFeO₃ nanoparticles, certain methods still face challenges such as the presence of trace secondary phases or the need for elevated calcination temperatures to attain complete crystallization and structural integrity. In the present work, we examine the use of ethylenediaminetetraacetic acid (EDTA) as a complexing agent in the sol-gel auto-combustion synthesis of LaFeO₃ nanoparticles. EDTA is a well-known multidentate ligand, possessing four carboxylic acid groups and two amine groups, which enables it to form stable chelate complexes with metal ions. This strong chelating ability allows EDTA to effectively bind with La³⁺ and Fe³⁺ ions, leading to the formation of a homogeneous and stable metal-ligand network in the sol-gel matrix. The presence of EDTA plays a crucial role in enhancing the gelation process, improving the distribution of metal ions, and ensuring better molecularlevel mixing of the precursors. As a result, this promotes enhanced phase purity and improved compositional uniformity of the final product. Moreover, the combustion behavior of the EDTA-assisted gel facilitates the removal of organic residues during calcination, enabling the formation of phase-pure LaFeO₃ nanoparticles at relatively lower temperatures compared to conventional methods. The synthesized materials characterized by X-Ray diffraction (XRD) and retvield refinement has been done using Fullprof software.

Experimental 2.1 Synthesis Process

To prepare LaFeO₃ nanoparticles, lanthanum nitrate hexahydrate [La(NO₃)₃•6H₂O] and ferric nitrate nonahydrate [Fe(NO₃)₃•9H₂O] were first dissolved separately in distilled water in their respective stoichiometric ratios. The two solutions were then combined to form a homogeneous precursor solution. Following this, ethylenediaminetetraacetic acid (EDTA) was introduced into the mixed precursor solution in a 1:1 molar ratio with respect to the total metal ions (La³⁺ + Fe³⁺). The mixture was continuously stirred and heated at approximately 100°C to promote complexation between the metal ions and EDTA. This process was maintained until the majority of the solvent had evaporated and the solution gradually transformed into a viscous, gel-like mass. Upon further heating, this gel underwent self-sustained auto-combustion, resulting in the formation of a puffy, porous precursor powder due to the rapid release of gases during combustion. The obtained powder was then calcined in a muffle furnace at 450°C for 2.5 hours to remove residual organics and to facilitate the formation of well-crystallized LaFeO₃ nanoparticles. The overall synthesis route for the EDTA-assisted sol-gel autocombustion process is illustrated schematically in Figure 1.

Characterization technique

The phase purity and crystalline structure of the calcined LaFeO₃ powders were analyzed using X-ray diffraction (XRD), performed on a PANalytical X'Pert Pro diffractometer operating at 40 kV and 40 mA, utilizing Ni-filtered Cu Kα radiation (λ = 0.15406 nm). XRD patterns were recorded over a 2θ range of 20° to 70°, with a step size of 0.02° and a scanning rate of 2° min⁻¹ to ensure highresolution data acquisition. To obtain detailed structural information, the diffraction data were subjected to Rietveld refinement using the FullProf Suite software, employing the orthorhombic Pbnm (space group no. 62) as the structural model. Furthermore, the magnetic behavior of the synthesized LaFeO₃ nanoparticles was examined by recording the magnetization (M) response to varying magnetic fields (H) at both room temperature (300 K) and at 5 K. These measurements were performed using a superconducting quantum interference device (SQUID) magnetometer (Quantum Design, San Diego, CA), known for its exceptional sensitivity to weak magnetic signals.

Results and Discussion

3.1 X-ray diffraction X-ray diffraction (XRD) serves as a powerful tool for evaluating the crystallinity, crystalstructure, and phase purity of synthesized materials. The XRD pattern of LaFeO₃ powders calcined at 450°C for 2.5 hours is presented in Figure 2. 111), ( 121), ( 210), ( 112), ( 220), ( 131), ( 202), ( 212), ( 103), ( 311), ( 240), ( 331) and (242) crystal planes, respectively. These peaks are in good agreement with the standard reference data from JCPDS Card No. 75-0541, confirming the formation of single-phase orthorhombic LaFeO₃ with Perovskite-type structure. The absence of any secondary peaks in the pattern further supports the phase purity of the synthesized material. Moreover, the notable broadening of the diffraction peaks indicates the nanocrystalline nature of the LaFeO₃ powders, consistent with the low-temperature synthesis approach employed in this study. These results confirm that phasepure LaFeO₃ with well-defined crystallinity was successfully achieved at a relatively low calcination temperature of 450°C. The average crystallite size (D) of LaFeO 3 was calculated using Scherrer's which is given follow

Where D is crystallite size, K is equal to 0.89 Å, β is FWHM in radians, θ is the brags angle, λ is the X-ray wavelength (0.15406 nm). The average crystallite size (D) is found to be 25 nm which confirms the nanocrystalline nature of synthesized LaFeO 3 . The lattice parameters of the synthesized LaFeO₃ nanoparticles were determined through Rietveld refinement of the XRD data. Figure 3 presents the results of the Rietveld analysis for LaFeO₃ nanoparticles prepared using citric acid at 450 °C. The XRD data were refined assuming an orthorhombic crystal structure with the Pbnm space group, which accurately accounts for all diffraction peaks associated with the LaFeO₃ perovskite phase. The structural parameters obtained from this refinement are summarized in Table 1 and show good consistency with previously reported values for LaFeO₃ nanoparticles [14] . A strong agreement between the observed and calculated patterns is indicated by χ² = 2.02, and R-factors of Rwp = 13.6, Rp = 12.1, RBragg = 5.38, and RF-factor = 5.38. The refined lattice parameters were found to be a = 5.546 Å, b = 5.561 Å, c = 7.852 Å, with α = β = γ = 90°, and a unit cell volume of 242.197 ų, which aligns well with reported literature values for LaFeO₃ nanoparticles [14] . The crystal structure of LaFeO₃, based on the refined crystallographic data, was visualized using VESTA software and is shown in Figure 3. Fe-O1-Fe ( 0 ) -157.08(0) Fe-O2 (Å) -2.01(0) Fe-O2-Fe ( 0 ) -154.04 (0)

Magnetic Properties

The magnetic characteristics of the prepared LaFeO₃ nanoparticles were evaluated at 5 K and 300 K under an applied field ranging from -70 kOe to +70 kOe. , where M + and M -are upper and lower remanence, respectively [44] . The coercivity values of pure LaFeO 3 nanoparticles at 5K and 300K were found to be 880 and 3450 Oe, respectively. From the hysteresis loop, M r Values were found to be 0.03 and 0.07 emu/g at 5 K and 300 K, respectively. The magnetization at maximum applied field (Ms) were 0.95 and 0.81 emu/g at 5 K and 300 K, respectively. This M-H behavior in LaFeO 3 nanoparticles are different from the linear behavior of bulk antiferromagnetic LaFeO 3 [16,45,46] . The M-H hysteresis loop suggests the presence of two magnetic phases in the synthesized LaFeO 3 nanoparticles. Furthermore, the roomtemperature M-H curve exhibits a broader loop compared to the low-temperature curve, which has a higher coercive magnetization. The large values of coercivity indicate the presence of high anisotropy, and surface defects in prepared LaFeO 3 nanoparticles. It has been reported that at nanoscale, antiferromagnetic systems such as NiO [47,48] , CuO [49] , Co 3 O 4 [50] and BiFeO 3 [51] shows the weak ferromagnetic behavior along with dominant antiferromagnetic behavior. According to Néel's model for small antiferromagnets, the spins of the two ferromagnetic sublattices in the antiferromagnetic lattice are not completely balanced due to their small size and surface defects [52] . This imbalance in ferromagnetic spin sublattices at the surface of LaFeO 3 nanoparticles leads to uncompensated spins and results in net magnetic moment. The presence of "uncompensated" surface spin surrounding the LaFeO 3 antiferromagnetic nanoparticles is further confirmed by shifted M-H hyteresis loop at low temperature. It should be noted in the magnified view of Fig. 7b that (at 5K) the M-H hysteresis loop shifts toward the positive magnetization axis and negative magnetic field axis, a behavior not observed in the room-temperature M-H loop. This result suggests that magnetic unidirectional anisotropy can be isothermally induced at room temperature during the initial magnetization, likely arising from interfacial coupling between the ferrimagnetic and antiferromagnetic phases present in the LaFeO₃ nanoparticles. This intrguing feature of shifted hysteresis loop is khown as exchange bias effect which is a charateristic of hybrid antiferromagnetic-ferromagnetic (AFM/FM) systems. Therefore, the M-H hysteresis loop of LaFeO₃ nanoparticles unveil a superposition of contribution attributed to AFM core and FM component arises from uncompensated surface spins as a result LaFeO₃ nanoparticles consist of AFM cores and FM-like shells [43,45,53] . At room temperature, the magnetic properties of LaFeO₃ nanoparticles are primarily influenced by the antiferromagnetic core, while at low temperatures, surface spins become dominant, leading to the formation of a spin glass state.

Conclusions

In summary, we have presented a simple methodology for the synthesis of single phase LaFeO₃ nanoparticle using the Sol-Gel auto-combustion technique with EDTA as the complexing agent. XRD analysis along with Rietveld refinement confirms the formation of phase-pure orthorhombic perovskite-type LaFeO₃ with Pbnm (62) space group and having average crystallite size of is ~ 25 nm. The magnetic measurements suggested the presence of antiferromagnetic phase along with weak ferromagnetic phase and M-H loop exhibited high coercivity values of 880 Oe and 3450 Oe at 5K and 300K, respectively. The LaFeO₃ nanoparticle are composed of FM shells and AFM cores because of uncompensated surface spins. The shifted hysteresis at low temperature suggested the presence of exchange bias in LaFeO₃ nanoparticle which has great applications in spitronics.

Acknowledgement

All authors sincerely appreciate the support of the University Department of Chemistry, Lalit Narayan Mithila University, Darbhanga. Additionally, one of the authors, SKS, expresses gratitude to the University Grant Commission (UGC), New Delhi, India, for providing the BSR start-up grant that facilitated this research work.

References

1. Wiranwetchayan O, Yodyingyong S, Sagawa T, Imai H, Sreethawong T. Characterization of perovskite LaFeO3 synthesized by microwave plasma method for photocatalytic applications. Ceram Int. 2019;45(4):4802-4809.
2. Zhang Y, Zhang Q, Lu X, Xu J, Chen Y. Formaldehyde-sensing properties of LaFeO3 particles synthesized by citrate sol-gel method. J Sol-Gel Sci Technol. 2016;79(1):167-175.
3. Hao P, Li X, Tang Y, Zhou J, Wang L. Hydrothermal preparation and acetone-sensing properties of Ni-doped porous LaFeO3 microspheres. J Mater Sci Mater Electron. 2020;31(9):6679-6689.
4. Humayun M, Raziq F, Zada A, Khan A, Qu Y, Jing L. Perovskite-type lanthanum ferrite based photocatalysts: Preparation, properties, and applications. J Energy Chem. 2022;66:314-338.
5. Zhang M, Guo Y, Zhao H, Xu Z, Liu Q. Enhanced ferroelectric, magnetic and magnetoelectric properties of multiferroic BiFeO3-BaTiO3-LaFeO3 ceramics. Ceram Int. 2018;44(17):21269-21276.
6. Dedon LR, Karthik J, Asta M, Martin LW. StrainDriven Nanoscale Phase Competition near the Antipolar-Nonpolar Phase Boundary in Bi0.7La0.3FeO3 Thin Films. ACS Appl Mater Interfaces. 2018;10(17):14914-14921.
7. Noroozifar M, Khorasani-Motlagh M, Akbari R, Khoshsafar H. Enhanced electrocatalytic properties of Pt-chitosan nanocomposite for direct methanol fuel cell by LaFeO3 and carbon nanotube. J Power Sources. 2014;248:130-139.
8. Sivakumar N, Rani BJ, Vidhya R, Ramachandran K, Natarajan S, Ganesan R. Crystal structure, dielectric and magnetic studies of pure and Sr substituted LaFeO3 single crystal grown by optical floating zone technique. J Alloys Compd. 2023;943:169161.
9. Wang Z, Huang J, Sun G, Xu Y, Wu H, Liu H. Dielectric and ferroelectric properties of LaFeO3 particles derived from metal organic frameworks precursor. Ceram Int. 2019;45(2 Pt A):1825-1830.
10. Lin Q, Li Y, Lu Y, Cheng J, Du X. The effects of Mg2+ and Ba2+ dopants on the microstructure and magnetic properties of doubly-doped LaFeO3 perovskite catalytic nanocrystals. Ceram Int. 2019;45(3):3333-3340.
11. Koehler W, Wollan E. Neutron-diffraction study of the magnetic properties of perovskite-like compounds LaBO3. J Phys Chem Solids. 1957;2(2):100-106.
12. Natali Sora I, Fornasini ML, De Julián Fernández C, Greneche JM. Crystal structures and magnetic properties of strontium and copper doped lanthanum ferrites. J Solid State Chem. 2012;191:33-39.
13. Yao Q, Zhu L, Zheng Z, Ma J, Zhang J. Antiferromagnetic-ferromagnetic transition in Bi-doped LaFeO3 nanocrystalline ceramics. Ceram Int. 2020;46(12):20472-20476.
14. Ateia EE, Abbas MA, Nofal MM, Mohamed MA. Structural and Magnetic Tuning of LaFeO3 Orthoferrite Substituted Different Rare Earth Elements to Optimize Their Technological Applications. J Inorg Organomet Polym Mater. 2021;31(4):1713-1725.
15. Haque A, Miah MI, Nayan MM, Khan KA, Islam A. Effects of Bi doping on structural and magnetic properties of cobalt ferrite perovskite oxide LaCo0.5Fe0.5O3. Ceram Int. 2022;48(11):1634816356.
16. Sharma P, Srivastav SK, Chatterjee R. Evidence of two dimensional dilute antiferromagnet mediated exchange bias field and vertical shift in LaFeO3-NiO nanocomposite. J Magn Magn Mater. 2021;523:167619.
17. Sun J, Rao G, Liang J. Crystal structure and electronic transport property of perovskite manganese oxides with a fixed tolerance factor. Appl Phys Lett. 1997;70(14):1900-1902.
18. Shikha P, Kang TS, Randhawa BS. Effect of different synthetic routes on the structural, morphological and magnetic properties of Ce doped LaFeO3 nanoparticles. J Alloys Compd. 2015;625:336-345.
19. Sedumathavan K, Joseph A, Sakunthala K, Sundaram R, Ramachandran K, Natarajan S. A comprehensive exploration of pure and Zn doped LaFeO3 nanoparticles synthesized by solid state mechanism for charge storage devices. J Mater Sci Mater Electron. 2024;35(27):1791.
20. Imam N, Suresh KG, Phase DM, Choudhury D. Correlation between structural asymmetry and magnetization in Bi-doped LaFeO3 perovskite: a combined XRD and synchrotron radiation XAS study. J Mater Sci Mater Electron. 2021;32:3361-3376.
21. Rini EG, Ramesh V, Narayanan V, Stephen A. Correlation of octahedral distortion with vibrational and electronic properties of LaFe1-xTixO3 nanoparticles. J Alloys Compd. 2020;830:154594.
22. Kumar S, Singh RK, Kharabe RG, Pandey OP. The effect of aliovalent Pb2+ dopant on the magnetic and magneto dielectric properties of LaFeO3 solid solutions. J Magn Magn Mater. 2018;467:89-95.
23. Cao E, Lu Q, Wang Z, Wang Y. Effect of synthesis route on electrical and ethanol sensing characteristics for LaFeO3-δ nanoparticles by citric sol-gel method. Appl Surf Sci. 2017;393:134-143.
24. Ali FA, Al-Mamari R, Adeosun WA, Alharthi NH, Alothman ZA. Facile synthesis of porous LaFeO3 hexagons for acetone sensing. Mater Today Proc. 2023;74:993-1001.
25. Lakshminarayanan N, Kiebach R, Hendriksen PV, Larsen PH. Doped LaFeO3 as SOFC catalysts: Control of oxygen mobility and oxidation activity. Catal Today. 2010;157(1-4):446-450.
26. Kumar M, Kumar A, Sinha AS, Kaur A. Synthesis of pure and Sr-doped LaGaO3, LaFeO3 and LaCoO3 and Sr, Mg-doped LaGaO3 for ITSOFC application using different wet chemical routes. Mater Chem Phys. 2009;113(2-3):803-815.
27. Althomali RH, Adeosun WA. Wet chemically synthesized metal oxides nanoparticles, characterization and application in electrochemical energy storage: An updated review. Synth Met. 2023;298:117424.
28. Zhong Z, Jing ZJ, Xu Y. Highly sensitive acetone sensor based on LaFeO3 microspheres prepared by facile hydrothermal synthesis. J Nanoelectron Optoelectron. 2021;16(10):1511-1520.
29. Jiang W, Zhang Q, Wang H, Fang Y, Zhang W. Preparation of crystalline LaFeO3 nanoparticles at low calcination temperature: Precursor and synthesis parameter effects. Materials (Basel). 2021, 14. DOI:10.3390/ma14195534
30. Houshiar M, Zebhi F, Naderi A, Askari Z, Arabi H. Synthesis of cobalt ferrite (CoFe2O4) nanoparticles using combustion, coprecipitation, and precipitation methods: A comparison study of size, structural, and magnetic properties. J Magn Magn Mater. 2014;371:4348.
31. Gabal M, Al Angari YM, Alzaid M, El-Dek SI. Autocombustion synthesis and characterization of perovskite-type LaFeO3 nanocrystals prepared via different routes. Ceram Int. 2019;45(13):16530-16539.
32. Ahmed M, Azab A, El-Khawas E. Structural, magnetic and electrical properties of Bi doped LaFeO3 nanocrystals, synthesized by auto-combustion method. J Mater Sci Mater Electron. 2015;26(11):8765-8773.
33. Bhat I, Dhiman P, Sharma P, Kotnala RK, Singh M. Effect of Zn doping on structural, magnetic and dielectric properties of LaFeO3 synthesized through sol-gel auto-combustion process. Mater Res Bull. 2013;48(11):4506-4512.
34. Reddy NM, Srinivasula P, Venugopal R, Ramana MV. Collating the structural, vibrational, and photocatalysis properties of LaFeO3 rare-earth orthoferrite nanoparticles synthesized by the sol-gel method. J SolGel Sci Technol. 2024, 1-9.
35. Sukumar M, Rao PV, Sundaram R, Reddy KR, Natarajan S. Facile synthesis of Fe3+ doped La2CuO4/LaFeO3 perovskite nanocomposites: Structural, optical, magnetic and catalytic properties. Mater Sci Semicond Process. 2019;100:225-235.
36. Kostyukhin EM, Kustov AL, Kustov LM. One-step hydrothermal microwave-assisted synthesis of LaFeO3 nanoparticles. Ceram Int. 2019;45(11):14384-14388.
37. Mehdizadeh P, Askari M, Ghaedi M, Asfaram A. Effective removal of organic pollution by using sonochemical prepared LaFeO3 perovskite under visible light. Ultrason Sonochem. 2020;61:104848.
38. Alkahtani SA, Alharthi NH, Alothman ZA, Adeosun WA. Sonochemical synthesis of lanthanum ferrite nanoparticle-decorated carbon nanotubes for simultaneous electrochemical determination of acetaminophen and dopamine. Microchim Acta. 2024;191(1):25.
39. Phokha S, Swatsitang E, Sreekantan S, Maensiri S. Structure, optical and magnetic properties of LaFeO3 nanoparticles prepared by polymerized complex method. J Sol-Gel Sci Technol. 2014;71(2):333-341.
40. Gomez-Cuaspud JA, Schmal M. Nanostructured metal oxides obtained by means polymerization-combustion at low temperature for CO selective oxidation. Int. J Hydrogen Energy. 2013;38(18):7458-7468.
41. Giannakas A, Ladavos A, Pomonis P. Preparation, characterization and investigation of catalytic activity for NO+ CO reaction of LaMnO3 and LaFeO3 perovskites prepared via microemulsion method. Appl Catal B Environ. 2004;49(3):147-158.
42. Abazari R, Sanati S. Perovskite LaFeO3 nanoparticles synthesized by the reverse microemulsion nanoreactors in the presence of aerosol-OT: Morphology, crystal structure, and their optical properties. Superlattices Microstruct. 2013;64:148-157.
43. Gabal M, Alzaid M, Al Angari YM. Sucrose autocombustion synthesis of Al3+ and Cr3+ substituted LaFeO3 ceramic perovskite: Structural, magnetic, and electrical characterizations. Results Chem. 2025, 102126.
44. Huang X, Du Y, Yang L, Li X, Zhao J. Size-dependent exchange bias in La0.25Ca0.75MnO3 nanoparticles. Phys Rev B. 2008;78(22):224408.
45. Zamora J, Cano R, Recio FJ, González J, Alonso J. Magnetic/optical assessments of RFeO3 (R= La, Pr, Nd, and Sm) ceramics: An experimental and theoretical discernment. J Alloys Compd. 2024;971:172646.
46. Al-Mamari R, Adeosun WA, Alkahtani SA, Alothman ZA. Core and surface structure and magnetic properties of mechano-synthesized LaFeO3 nanoparticles and their Eu3+-doped and Eu3+/Cr3+-co-doped variants. Sci Rep. 2024;14(1):14770.
47. Rahal H, Belkacem R, Boukoussa B, Trari M. Synthesis, characterization, and magnetic properties of pure and EDTA-capped NiO nanosized particles. J Nanomater. 2017;2017(1):7460323.
48. Jafari A, Ghasemi E, Shoja Razavi R, Mozaffari HR, Soltani M. Evolution of structural and magnetic properties of nickel oxide nanoparticles: Influence of annealing ambient and temperature. J Magn Magn Mater. 2019;469:383-390.
49. Batsaikhan E, Kim HJ, Kim K, Seo WD. Largely enhanced ferromagnetism in bare CuO nanoparticles by a small size effect. ACS Omega. 2020;5(8):3849-56.
50. Yetim NK. Hydrothermal synthesis of Co3O4 with different morphology: Investigation of magnetic and electrochemical properties. J Mol Struct. 2021;1226:129414.
51. Srivastav SK, Sharma P, Chatterjee R, Kotnala RK. Presence of glassy state and large exchange bias in nanocrystalline BiFeO3. J Magn Magn Mater. 2017;441:503-510.
52. Néel L. Some new results on antiferromagnetism and ferromagnetism. Rev Mod Phys. 1953;25(1):58.
53. Mukhopadhyay K, Mahapatra AS, Chakrabarti PK. Multiferroic behavior, enhanced magnetization and exchange bias effect of Zn substituted nanocrystalline LaFeO3 (La(1-x)ZnxFeO3, x=0.10, and 0.30). J Magn Magn Mater. 2013;329:133-141.