Magnetic Properties of Mixed Valence La(AgSr)MnO3 Manganites Obtained by Solid‐State Reaction Method

In this work, we present a systematic study on the effect of monovalent and divalent cation inclusion on the magnetic properties of the manganites series La_0.80(Ag_1?xSr_x)_0.20MnO₃ (x = 0.0–1.0) synthesized by the solid‐state reaction method. The decreasing Sr:Ag proportion across the compositional series was verified by X‐ray photoelectron spectroscopy. Concerning magnetic properties, the hysteresis curves manifested an initial paramagnetic response at x = 0.0, followed by a progressive ferromagnetic behavior with an optimum Ag:Sr ratio at x = 0.75, for which an enhanced saturation magnetization of 51 Am²/kg and a Curie temperature of 336 K were recorded. Results are explained on the basis of the effect of the increasing unit cell volume on the double exchange interaction between magnetic Mn³⁺– Mn⁴⁺ atoms.     

Electrical transport properties driven by magnetic competition in hole-doped perovskite Pr1-xBaxMnO3 (0.25 ≤ x ≤ 0.36)

In this work, polycrystalline Pr_1-xBa_xMnO₃ (0.25 ≤ x ≤ 0.36) ceramics were synthesized, and their magnetic and electrical transport properties were systematically studied. All samples show two metal-insulator transitions (MITs) corresponding to the high temperature T_MI1 and low temperature T_MI2, respectively, besides the non-Griffith phase above the ferromagnetic (FM) transition temperature T_C. Combining the results of the transport and magnetic properties, it is found that the FM transition temperature T_C coincides with the temperature T_MI1, which is linearly related to the A-site ionic radius mismatch variance σ², indicating the enhancement of FM interactions due to the increase of the degree of B-site ordering of Mn³⁺/Mn⁴⁺ ions. The positive correlation between ferromagnetic insulators (FMI) and magnetic interactions, including the FM and short-range antiferromagnetic (AFM) interactions, is confirmed. It is suggested that the first MIT at T_MI1 is attributed to the Mn³⁺/Mn⁴⁺ double exchange interactions and the second MIT at T_MI2 is closely related to the suppression of the AFM interactions under the internal FM field induced by the Mn³⁺/Mn⁴⁺ DE interactions. This work provides not only a theoretical understanding on the origin of MIT at low temperature, but also a new way for adjusting the FMI in perovskite manganese oxide Pr_1-xBa_xMnO₃ for application.     

Structural analysis and electrode performance of Ce doped SrMnO3 synthesised by EDTA citrate complexing process

Abstract

Sr_1?xCe_xMnO₃ (SCM, 0·1≤x≤0·4) powders were synthesised by an ethylenediaminetetraacetic acid citrate complexing process, and their properties were investigated. The synthesised Sr_1?xCe_xMnO₃ powders showed a pure perovskite phase, whereas the composition with x?=?0·4 had second phases. The unit cell volumes increased with increasing Ce content because substituted Ce ions formed some Mn³⁺ ions, which have a larger ionic radius than Mn⁴⁺. The electrical conductivity improved with increasing Ce content up to x?=?0·3 (291 S cm^?1 at 750°C), revealing a double exchange interaction. Although the electrical conductivity was increased by doping Ce ions, the polarisation resistance increased due to the increase in lattice distortion with doping Ce content. The substitution of Ce ions for Sr in SrMnO₃ led to the formation of larger Mn³⁺ ions than Mn⁴⁺ ions and lattice distortion, which would affect the electrical and oxygen ion conductivity.     

Percolation like transitions in phase separated manganites La0.5Ca0.5Mn1-xAlxO3-δ

We show that the replacement of Mn with Al strongly affects the magnetization and electrical transport behaviors in La_0.5Ca_0.5Mn_1-xAl_xO_3-δ (x = 0, 0.05, 0.07 and 0.09). Nonmagnetic Al³⁺ ions substitution at Mn sites dilutes Mn³⁺-O^2--Mn⁴⁺ network, thus suppresses the ferromagnetic metallic state in La_0.5Ca_0.5MnO_3-δ and causes a phase separation phenomenon, in which ferromagnetic phase coexists with antiferromagnetic charge ordered phase at low temperatures. With applying sufficiently high magnetic field, step-like metamagnetic transitions were observed in x = 0.05–0.09 systems below helium temperature, in which the antiferromagnetic charge ordered phase collapsed into ferromagnetic phase. Corresponding to the sharp step-like metamagnetic transitions, the resistivity decreases dramatically with increasing magnetic field, exhibiting a percolative insulator-metal transition. The variation of temperature and magnetic field changes the relative fractions of ferromagnetic and charge ordering phases, and percolative insulator-metal transition occurs due to the development of percolation paths between the growing FM domains.     

XAS and XPS analysis of double magnetic transition,canonical spin glass behavior and magnetoresistance in LaMn1-xCoxO3 (0.1 ≤ x ≤ 0.5) system

Polycrystalline LaMn_1-xCo_xO₃ (0.1≤ x ≤ 0.5) samples were synthesized using conventional ceramic method. Rietveld refined X-ray diffraction pattern revealed the single-phase orthorhombic crystal structure of all the samples with the space group Pbnm. Temperature-dependent magnetic measurements performed in field cooled (FC) and zero field cooled (ZFC) mode at 10² Oe exhibit the onset of double transition in x = 0.3–0.5 compositions. The ordering temperature rises with an increase in Co concentration. FC and ZFC studies show the presence of glassy state below the ordering temperature in all samples; confirmed using a. c. susceptibility measurements. The a. c. susceptibility data are analyzed using power law and the existence of canonical spin glass is revealed. Magnetic hysteresis studies demonstrate the enhanced ferromagnetism amid the presence of unsaturated magnetization with an increase in Co doping. The presence of double transition and spin glass state is attributed to the competing ferromagnetic and anti-ferromagnetic interactions between the Co and Mn ions present in the system. The system also depicts the presence of appreciable value of magnetoresistance ~42% at 8 T magnetic field in x = 0.5 sample. These properties are interpreted through valence and spin states of Mn and Co ions, being confirmed from electronic structure studies using X-ray absorption spectroscopy (XAS) at L_3,2- edges of respective ions along with O K-edge for all samples (0.1≤ x ≤ 0.5). After meticulous analysis and conjoining the results obtained from magnetization and XAS studies, it is found that cobalt is present in high spin Co²⁺ and high/low spin Co³⁺-state. Charge transfer multiplet calculation done at L_3,2 edges of Mn and Co ions confirm the presence of Mn³⁺/Mn⁴⁺ and Co²⁺/Co³⁺ states consistent with XAS results. X-ray photoelectron spectroscopy performed at Mn2p, Co2p, and O1s -edges further substantiate the reasons behind the properties exhibited by the present system.     

Structural,electrical, and magnetic transport properties of La0.72Ca0.28Mn1−xCrxO3 (0 ≤ x ≤ 0.06) ceramics

To obtain comprehensive materials with both high temperature coefficient of resistivity (TCR) and magnetoresistance (MR) at low magnetic fields, polycrystalline La_0.72Ca_0.28Mn_1?xCr_xO₃ (x = 0, 0.02, 0.04, 0.06) ceramics were prepared herein by sol–gel method. Electronic configuration of Cr³⁺ ions is similar to that of Mn⁴⁺ ions, therefore, successive substitution of Mn with Cr increases electrical resistivity and decreases metal–insulator transition temperature of ceramics, even yielding hump-like feature for Cr-rich (x = 0.06) samples. The best TCR (28.50%·K^?1) and MR (72.37%) values were obtained simultaneously at Cr dopant content of 0.02 (La_0.72Ca_0.28Mn_0.98Cr_0.02O₃). Strong response of the material to temperature and magnetic field was caused by minimal symmetry of orthorhombic structure and the most robust Jahn–Teller distortion. With increasing Cr content, Mn³⁺/Mn⁴⁺ or Mn³⁺/Cr³⁺ double exchange was diluted, and Cr³⁺/Cr³⁺ or Cr³⁺/Mn⁴⁺ superexchange was promoted. However, the internal competition effect was not conducive to the improvement of material properties.     

Magnetic properties of Cu1+xMn2−xO4 and Ni1+xMn2−xO4 solid solutions

Magnetic properties of two spinel oxides solid solutions, Cu_1+xMn_2−xO₄ and Ni_1+xMn_2−xO₄, are reported. These series are characterized by two magnetic transitions: the upper one, of ferrimagnetic type, occurs at about 85 K (for copper-based) and at 105–110 K (for nickel-based spinels), independently of the x-content; the lower transition may be related to a Néel-type collinear ordering and takes place at 30 and 45 K, respectively. Application of moderate fields (H > 250 Oe) make both transitions to merge into one broad maximum in the magnetization, which takes place at lower temperature when applying larger fields. Magnetization cycles with temperature (ZFC/FC) or field (loops) allowed us to well characterize the ordered state. The effective moment follows the expected behavior when manganese ions are being substituted by ions of lower magnetic moment (Ni²⁺ and Cu²⁺).     

Tuning of conductive type and magnetic properties of Ca3Co2O6 ceramics through Pb‐doping

The effect of Pb doping on structural, electrical, magnetic, and thermal transport properties of Ca_3?xPb_xCo₂O₆ (x=0‐0.3) ceramics has been investigated systemically. It is found that the substituted Pb‐ions have a mixed valence state of +2 and +4, and a small amount of Co³⁺ ions will transfer into Co²⁺ due to the substitution of Pb⁴⁺ for Ca²⁺. The resistivity decreases monotonically with increasing Pb content, which is related to the variation in carrier concentration and the enhanced grain connectivity. The signs of both Hall coefficient and thermopower changed from positive to negative by a proper Pb doping, indicating the conductive type of Ca₃Co₂O₆ can be effectively tuned from p to n through the doping. The low‐temperature magnetization, the magnetic exchange coupling constant J and Weiss temperature θ decrease monotonically with the increase in Pb‐doping content, indicating the strength of the ferromagnetic interaction between adjacent high spin Co³⁺ ions has been weakened due to the reduced magnetic correlation length in these Pb‐doped samples.     

Effect of manganese stoichiometry at B-site on magneto-transport and magnetic properties of La0.67Sr0.33MnO3manganites

To study the effect of manganese non-stoichiometry at B-site, a series of manganites with compositional formula La_0.67Sr_0.33Mn_1±xO₃ (where x = 0, 0.05 and 0.1) was synthesized by oxalate precursor method. X-ray diffraction data confirm the rhombohedral structure of La_0.67Sr_0.33Mn_1±xO₃ along with minor phases of Mn₃O₄. The average grain size is found to be 266 nm for x = 0 whereas its magnitude decreases with excess or deficiency in manganese concentration. An increase in the manganese non-stoichiometry leads to the coexistence of ferromagnetic and antiferromagnetic interactions. The effect of Mn_1±x on the magnetotransport properties could be understood on the basis of collective behaviour of magnetic spins, double exchange mechanism and ratio of Mn⁴⁺/Mn³⁺ ions. A crossover from negative to positive magnetoresistance behavior above metal-insulator transition temperature was observed for LSP-0.95 sample, whereas a positive magnetoresistance over the entire temperature region was noticed for LSP-1.10 sample.     

Dynamical behavior of step-like transition of La0.5Sr0.5Mn1−xTixO3 in a widened field sweep rate

The magnetization behavior of Ti⁴⁺ doped perovskite manganites La_0.5Sr_0.5Mn_1−xTi_xO₃ (x=0.15, 0.175 and 0.2) was investigated. Experimental results show that Ti⁴⁺ dopant suppresses the antiferromagnetic charge ordering and leads to a step-like magnetization behavior below 3 K. The step-like transitions and the critical magnetic fields are strongly dependent on the Ti doping level, magnetic field sweep rate and temperature. Above 3 K, the step-like transitions transform to broad ones. In addition, under pulsed high magnetic fields with an ultrafast field sweep rate of ~10³ T/s, the sharp step-like transitions observed in the static magnetization measurements become smooth metamagnetic transition at low temperatures. This feature is correlated with the collapse of the balance between the magnetic energy and elastic energy in the phase separation system within a martensitic-like scenario.     

Influence of Ag doping on electrical and magnetic properties of La0.625(Ca0.315Sr0.06)MnO3 ceramics

Polycrystalline Ag-doped [La_0.625(Ca_0.315Sr_0.06)MnO₃]_1-x:Ag_x (LCSMO) ceramics with (x = 0, 0.03, 0.05, 0.10, 0.15, and 0.20) were prepared by sol-gel method, and their structures and properties were characterized. X-ray diffraction results indicated that all bulk samples had single phase with orthorhombic phase (space group of Pbnm) without impurities. With the increase of Ag doping content, the resistivity of the samples decreased, while the remanent magnetization and coercive field increased. The metal to insulator transition temperature (T_p), temperature coefficient of resistance (TCR) and Curie temperature (T_c) for x = 0.20 were determined as 300 K, 9.38% (292.6 K) and 291.86 K respectively. The highest MR value of 28.36% (295.03 K) was obtained at x = 0.15. XPS data revealed that substitution between A-site ions and Ag⁺ could increase the ratio of Mn⁴⁺ ion. Double exchange effect (DE) enhanced by changing Mn–O bond distance, Mn–O–Mn bond angle, and increasing Mn⁴⁺ ion concentration. These features promoted the transfer of itinerant electron between Mn³⁺ and Mn⁴⁺ ions. However, the magnetization obtained at x = 0.20 was less than that at x = 0, as diamagnetic Ag released magnetism of the samples. The results suggested that the LCSMO polycrystalline ceramics could be used as a candidate to prepare room temperature infrared detectors, magnetic sensors or magneto-electric devices, and so on.     

Irreversible metamagnetic behaviors and H-T phase diagram in phase separated La0.5Ca0.5Mn1-xAlxO3-δ

Magnetization relaxation, ac susceptibility, dc magnetization and magnetoelectrical transport measurements have been carried out on Al³⁺-doped manganites La_0.5Ca_0.5Mn_1-xAl_xO_3-δ (x = 0.05, 0.07, 0.09, 0.10, 0.15). Experimental results suggest that nonmagnetic Al³⁺ substituting Mn suppresses the ferromagnetic phase and induces a charge ordered antiferromagnetic phase. The coexistence and competition of these two kinds of interactions result in a spin-glass like state in x = 0.1 and 0.15 system. Obvious hysteresis was observed in both magnetization and resistivity versus temperature and magnetic field curves, suggesting an inhomogeneous metastable phase transition. Upon applying a magnetic field of H_C^A-F, the Al³⁺-doped samples undergo an irreversible metamagnetic transition from the charge ordering antiferromagnetic insulating to ferromagnetic metallic phase in the low temperature region. Phase diagram in the H_C-T plane has been determined according to the magnetization and magnetoelectric transport measurements. The magnetic disorders and antiferromagnetic matrix produced by Al³⁺ dopants and spontaneous oxygen vacancies play an important role in the pinning of the FM phase.     

Investigation of structural,optical, electrical,and magnetic properties of Fe-doped La0.7Sr0.3MnO3 manganites

In this work, the physical properties of nanocrystalline samples of La_0.7Sr_0.3Mn_1−xFe_xO₃ (0.0 ≤ x ≤ 0.20) perovskite manganites synthesized by the reverse micelle (RM) technique were explored in detail. The phase purity, crystal structure, and crystallite size of the samples were determined using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. All the samples had rhombohedral crystal structure and crystallite size increased with increase in Fe content in La_0.7Sr_0.3MnO₃. The scanning electron micrographs (SEMs) exhibited smooth surface morphology and nonuniform shape of the particles. The optical properties studied using UV-visible absorption spectroscopy revealed a decrease in the absorbance and optical band gap with an increase in Fe content in La_0.7Sr_0.3MnO₃ compound. The temperature-dependent resistivity measurements revealed semiconducting nature of x = 0 and 0.1 samples up to the studied temperature range, while a metal-to-insulator transition was observed at higher Fe doping. Magnetic studies revealed weak ferromagnetism in all the samples and a reduction in the maximum magnetization with an increase in Fe content. A close correlation between electrical transport and magnetic properties was observed with the doping of Fe ion in La_0.7Sr_0.3MnO₃ at Mn site. These results advocate strong interactions associated with the double exchange mechanism among Fe³⁺ and Mn³⁺ ions.     

Structure,magnetic, electrical transport and magnetoresistance properties of La0.67Sr0.33Mn1−xFexO3 (x=0–0.15) doped manganite coatings

We have undertaken a systematic study of the effect of Fe³⁺ doping on the crystal structure, magnetic, electrical transport and magnetoresistance properties of La_0.67Sr_0.33Mn_1−xFe_xO₃ (0≤x≤0.15) polycrystalline coatings prepared by the sol-gel and screen printing method. The X-ray powder diffraction and Reitveld refinement results indicate that the partial substitution of Mn³⁺ ions by Fe³⁺ ions does not introduce noticeable lattice distortion and structural transition. Magnetic measurements show that Fe³⁺ ions significantly lowers the Curie temperature, and the magnetization at low temperatures first increases and then decreases with further Fe³⁺ doping. The Fe³⁺ doped manganites (x>0.05) are semiconductors with high resistivity, as the consequence of low number of available hopping sites of charge carriers. The most stimulating result obtained is that the magnetoresistance property is greatly enhanced around the percolation threshold (x=0.05) of Fe³⁺ ions in this system and the percolative phase separation is responsible for the anomalous behavior.     

Synthesis and structural,magnetic characterization of nanocrystalline Zn1−xMnxO diluted magnetic semiconductors (DMSs) synthesized by combustion reaction

Nanocrystalline Mn²⁺ doped Zn_1−xMn_xO, where x=0.1, 0.15, 0.2, 0.25, 0.3 and 0.4 mol of Mn²⁺ diluted magnetic semiconductors (DMSs), were synthesized by the combustion reaction for spintronic applications. The effect of Mn²⁺ ion doping on the structural, morphological and magnetic properties of ZnO was investigated. The products of the reactions were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET), transmission electron microscopy (TEM), and magnetic measurements (VSM). XRD spectra data revealed the formation of a ZnO phase at all the Mn²⁺ doping concentrations used, indicating that the synthesis was efficient in diluting the Mn²⁺ ions in the ZnO lattice. Increasing the Mn²⁺ ion concentrations reduced the maximum reaction and ignition temperature and contributed to reduce crystallite and particle sizes. The samples showed the typical behavior of soft magnetic materials at all the Mn²⁺ concentrations evaluated here. The Curie temperature (Tc) was higher than room temperature at all the Mn²⁺ concentrations.     

Synthesis, structural and magnetic properties of nanostructured Ca0.9Gd0.1MnO3 obtained by modified glycine nitrate procedure (MGNP)

Ca_0.9Gd_0.1MnO₃ nanopowders with perovskite type crystal structure were synthesized by modified glycine nitrate procedure. Nanopowders were prepared by combining glycine with metal nitrates and/or metal acetates in their appropriate stoichiometric ratios. Modification of the procedure was performed by partial replacement of nitrates by acetates, in order to control the burn-up reaction. Obtained Ca_0.9Gd_0.1MnO₃ powders were calcinated in the temperature interval from 850 °C to 950 °C for 10 min. Properties such as phase evolution, lattice parameters, chemical composition and magnetic properties were monitored by DTA, X-ray diffraction, SEM/EDS and magnetic measurements. Magnetic measurements performed at the sample with the smallest crystallite size showed that a 10% of Gd³⁺ substituted Ca²⁺ ions changes antiferromagnetic properties of CaMnO₃ by the introduction of ferromagnetic interaction due to a double exchange between Mn³⁺ and Mn⁴⁺ ions. Presence of competing interactions and their randomness lead to a formation of a spin glass state below Neel temperature T_N = 110 K. From the high temperature magnetic susceptibility measurements effective magnetic moment of manganese ions is determined which lies between the values for Mn³⁺ and Mn⁴⁺ ions.     

Substitutional effect of Mg2+ on structural and magnetic properties of La2MgxNi1-xMnO6 double-perovskite thin films

By doping different concentrations of Mg²⁺ at Ni site, the (00l)-oriented La₂Mg_xNi_1-xMnO₆ (abbreviated as LM_xNMO, x = 0, 0.1, 0.2, 0.3, 0.4) double-perovskite thin films were epitaxially grown by pulsed laser deposition. The substitutional effect of Mg²⁺ on the structural and magnetic properties of the films is comprehensively investigated. It is found that with the increase of Mg-doping concentration, the in-plane and out-of-plane lattice constants as well as the cell volume of the LM_xNMO thin films increase, which could be ascribed to the radius difference between Mg²⁺ and Ni²⁺/Ni³⁺ ions, resulting in the in-plane compressive stress in LM_xNMO films. When the Mg-doping concentration is small (x ≤ 0.1), the doped Mg²⁺ tends to substitute Ni³⁺, which restrains the intensity of antiferromagnetic interaction between Ni³⁺-O-Mn³⁺, resulting in the reduced the exchange bias field as well as the increased the saturation magnetization. However, when the Mg-doping concentration increases to x ≥ 0.2, Mg²⁺ becomes to mainly replace Ni²⁺ position, which could inhibit the super-exchange ferromagnetic interaction between Ni²⁺-O-Mn⁴⁺ magnetic paths and thus reduce the saturation magnetization. The enhanced magnetic properties can be obtained in the LM_0.1NMO double-perovskite thin film, with a large saturation magnetization of 492.12 emu/cm³ and a high Curie temperature of 262.7 K.     

Tuning magnetic properties of BiFeO3 thin films by controlling Mn doping concentration

Mn-doped BiFeO₃ (BiFe_1–xMn_xO₃, x = 0, 0.03, 0.05, 0.10, 0.15 and 0.20) polycrystalline multiferroic thin films were successfully synthesized using the facile sol-gel spin-coating method. The crystal structures, surface features, elements valences, and magnetic properties of as-prepared samples were systematically explored. X-ray diffraction and Raman spectroscopy studies revealed the substitutions of Mn into the Fe site and a rhombohedral-to-orthorhombic phase transition. The Field Emission Scanning Electron Microscopy showed a decrease in the average particle sizes and an improvement of surface morphology with increasing the concentration of the substitutes. Energy-dispersive X-ray spectroscopy confirmed the doping concentration of Mn²⁺ in the samples. X-ray photoelectron spectroscopy indicated the co-existence of Mn²⁺/Mn³⁺ ions in the doped films. The remnant magnetization value of BiFe_0.90Mn_0.10O₃ thin film was found to be approximately six times than that of pure BiFeO₃ thin film under a magnetic field of 10 kOe. The enhanced magnetic property of BiFe_0.90Mn_0.10O₃ thin film was mainly ascribed to the structural distortion of spin cycloid and the enhancement of super-exchange interaction between the Fe³⁺ (Mn²⁺) and O^2- ions.     

Magnetic and magnetotransport properties of La1−xSrxMn0.5Сo0.5O3 perovskites

La_1?xSr_xMn_0.5Сo_0.5O₃ (x ≤ 0.75) perovskites have been studied as a function of temperature by neutron powder diffraction (NPD), magnetization and magnetoresistance measurements. The NPD data show that x = 0.15 and 0.5 compounds are stoichiometric, so the Sr²⁺ doping transforms Co²⁺ ions into the Co³⁺ ones, whereas manganese ions remain in the 4+ oxidation state as in the parent ferromagnetic compound ${\mathrm{LaCo}}_{\mathrm{0.5}}^{\mathrm{2}+}{\mathrm{Mn}}_{\mathrm{0.5}}^{\mathrm{4}+}{\mathrm{O}}_{\mathrm{3}}$. The magnetization data show a decrease in the Curie temperature from 215 K for the compound with x = 0 down to 147 K for the compound with x = 0.05. The compounds with x > 0.15 show an increase in T_C up to 260 K (x = 0.75) in spite of a gradual decrease of the spontaneous magnetization. The stoichiometric compound x = 0.5 demonstrates a sharp ferromagnet-paramagnet transition with T_C = 250 K. However, there is no visible coherent magnetic contribution to the NPD patterns. All compounds are semiconductors and exhibit large magnetoresistance gradually increasing with decrease of temperature. The magnetic data have been interpreted assuming that the Co³⁺ ions are in high spin state, however, there is a fraction of cobalt ions in low spin state. It is suggested that the superexchange interaction between Co³⁺ ions in the high spin state and Mn⁴⁺ ions is ferromagnetic and that the ferromagnetism of the compounds with x > 0.5 and high T_C is associated with positive exchange interactions between Co³⁺ being in high spin state and Mn⁴⁺ ions distributed within the short range regions. Based on the NPD results and magnetization data the magnetic phase diagram has been constructed.     

Finite size effect on Sm3+ doped Mn0.5Zn0.5SmxFe2−xO4 (0≤x≤0.5) ferrite nanoparticles

Samarium doped Mn–Zn ferrite nanoparticles of composition Mn_0.5Zn_0.5Sm_xFe_2−xO₄ (0≤x≤0.5) have been synthesized by a chemical co-precipitation method for developing low Curie temperature stable ferrofluid. These samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Electron Paramagnetic Resonance (EPR) spectroscopy and search coil method analytical techniques for their structural, morphological and magnetic properties. X-ray diffraction patterns confirmed the formation of crystalline single spinel phase of as grown nanoparticles. Lattice parameter and lattice strain increases with the increase in Sm³⁺ content. SEM images revealed the presence of ultrafine particles and their agglomerated structures in higher Sm³⁺ ions concentration analogues. The stoichiometry of the final product agreed well with the initial substitution composition as evidenced by EDS data. Electron paramagnetic resonance (EPR) spectra proved the ferromagnetic nature of nanoparticles. The magnetic measurements by search coil method showed superparamagnetism for x=0, 0.1 the samples with saturation magnetization of 23.95 emu/g for Mn_0.5Zn_0.5Fe₂O₄ sample which increases with rise in Sm³⁺ ions content. The results are explained and correlated with the structural, morphological and magnetic properties for developing stable kerosene based ferrofluid by using these nanoparticles.