Improvement of the Magnetization of Barium Hexaferrites Induced by Substitution of Nd<Superscript>3+</Superscript> Ions for Fe<Superscript>3+</Superscript> Ions

Barium hexagonal ferrites (BaNd _x Fe_12?x O ₁₉) have been synthesized by initial high-energy milling of the precursors and calcining subsequently. The as-prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). XRD and SEM examinations reveal that a high-crystallized hexagonal BaNd _x Fe_12?x O ₁₉ with lamellar morphology is obtained when the precursor is calcined at 1200^°C in air for 3 h. The hexagonal crystalline structure of BaFe₁₂ O ₁₉ is not changed after doping Nd³⁺ ions in BaFe₁₂ O ₁₉. However, lattice parameters a and b values increase with an increase in Nd content at first, then decrease. Nd substitution may improve the magnetic properties of BaNd _x Fe_12?x O ₁₉. BaNd_0.1Fe_11.9 O ₁₉, obtained at 1050^°C, has the highest specific saturation magnetization value (80.81 emu/g) and magnetic moment (16.21 μ _B); BaNd_0.2Fe_11.8 O ₁₉, obtained at 950^°C, has the highest coercivity value, 4075.19 Oe.     

The Effect of Annealing on Phase Stability and Magnetic Properties of Hexaferrite BaFe<Subscript>12</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>19</Subscript>

The hexaferrite BaFe₁₂ O ₁₉ phase was synthesized through the mechanical alloying process followed by subsequent annealing. Rietveld refinements of as-milled powder annealed at 700 ^°C confirm the formation of the BaFe₁₂ O ₁₉ phase with the presence of an important amount of the α-Fe₂ O ₃ phase. Thus, prior mechanical milling shows much lower reaction temperature and less reaction time compared to conventional methods. Further annealing up to 900 and 1100 ^°C could not enable the formation of a single BaFe₁₂ O ₁₉ phase, reaching an optimum phase composition ratio close to BaFe₁₂ O ₁₉/ α-Fe₂ O ₃ 70/30. The crystallite size was found to be in the nanoscale level but increases with increasing temperature (BaFe₁₂ O ₁₉ = 20–62 nm; α-Fe₂ O ₃ = 31–74 nm). SEM micrographs show that as the annealing temperature rises, the particles become more regular with sharp edges and hexagonal-like shapes. Magnetic measurements reveal that both M _s and M _r increase with annealing temperature to reach maximum values at 900 ^°C then remain unchanged, associated with phase composition. The coercivity H _c increases upon annealing up to 700 ^°C to a much higher value, from 1.7 kOe for as-milled powder to 4.8 kOe. Its value then decreases, attributed to grain (particle) growth (formation of larger particles) due to high annealing temperatures: 900–1100 ^°C. The obtained composites show very interesting magnetic properties and can be considered for potential applications, such as hyperthermia, heavy metal and dye removal, and hard/soft magnetic composites.     

Influence of the Preparation Conditions and Percolation Threshold on the Properties of Lead Zirconate Titanate/Cobalt Nickel Ferrite Magnetoelectric Composites

We have prepared magnetoelectric (ME) composite ceramics, free of foreign phases, in the lead zirconate titanate–cobalt nickel ferrite two-phase system: xPZT-36 + (100–x)Ni_0.9Co_0.1Fe₂O₄. The sol–gel derived ferrite powder used in our preparations seems to be doped with titanium cations from the PZT-36. The ceramics have a percolation threshold at x = 50–70 wt %, which is due to the increased electrical conductivity of Ni_0.9Co_0.1Fe₂O₄. As a consequence, the piezoelectric parameters of the ME ceramics drop sharply at x < 50–70 wt %: the piezoelectric moduli |d_ij| and piezoelectric voltage coefficients |g_ij| decrease by a factor of 3–5 in this composite range. The piezoelectric parameters |d_ij| and |g_ij| of the composites produced using the fine ferrite powder exceed those of the materials prepared using macrocrystalline Ni_0.9Co_0.1Fe₂O₄ powder by more than a factor of 2. The piezoelectric voltage coefficient g33 correlates with the ME coefficient ΔE/ΔH. The highest ME conversion efficiency (up to 45 mV/(cm Oe)) is offered by the 80 wt % PZT-36 + 20 wt % Ni_0.9Co_0.1Fe₂O₄ composites, whose composition lies in a subpercolation region. Even though the composites produced using the fine ferrite powder possess improved piezoelectric properties, they have smaller ΔE/ΔH coefficients (no greater than 25 mV/(cm Oe)), which can be tentatively attributed to the degradation of the properties of the ferrite as a consequence of doping with Ti⁴⁺ cations during the sintering of the composite ceramics.     

Investigation of Oxygen-Adsorbed Iron Pnictide Crystals

In this present study, we synthesized a new compound of YbFe₂As₂ crystals by using a melt growth technique. The YbFe₂As₂ crystals had been characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The presence of oxygen was found by EDAX on the surfaces of grown YbFe₂As₂ crystals which had been kept in air ambience for few months. The measurement of magnetization (M) versus temperature (T) using a superconducting quantum interference device (SQUID) at constant magnetic field (H = 100 Oe) for oxygen-adsorbed YbFe₂As₂ (YbFe₂As₂:O₂) had revealed an occurrence of sharp slope change around 140 K. An additional slope change had been observed around 40 K. We had carried out magnetization and transport measurements for oxygen-adsorbed YbFe₂As₂ (YbFe₂As₂:O₂) and oxygen-adsorbed BaFe₂As₂ (BaFe₂As₂:O₂) for comparative study also. M versus T data at H = 10,000 Oe had exhibited a paramagnetic behavior for both YbFe₂As₂:O₂ and BaFe₂As₂:O₂. The result of M versus H measurements at 2 K had shown that the saturation had not been achieved for YbFe₂As₂:O₂ at H = 80,000 Oe. There was a slope change observed in transport measurement for YbFe₂As₂:O₂ at 15 K which was not noticed for BaFe₂As₂:O₂.     

Influence of Al Substitution on Structural,Dielectric and Magnetic Properties of M-type Barium Hexaferrite

Polycrystalline Al-substituted BaFe₁₂O₁₉ samples were synthesized and investigated in order to study their structural, dielectric, and magnetic properties. Analysis of powder X-ray diffractions by Rietveld refinement shows the single-phase nature of samples with hexagonal structure. The magnetic properties of the samples were investigated by measuring temperature and field variations of magnetization using vibrating sample magnetometer. The temperature variation of magnetization measurement shows that all samples exhibit ferrimagnetic transition, and the transition temperature is found to decrease from 720 K for x = 0 to 709 K for x = 0.08. The saturation magnetization value at room temperature is found to decrease with increase in Al concentration, and on the other hand, the coercivity is found to increase. The dielectric spectrum of pure and Al-doped samples shows the typical exponential fall in dielectric constant with increase in frequency. The magnitude of dielectric constant at 100 Hz falls from 2000 for x = 0 to 400 for x = 0.10. The permeability spectrum of Al-doped samples is found to be almost independent of frequency for f>100 MHz.     

The Role of Mn–Mg–Ti–Zr Substitution on Structural and Magnetic Features of BaFe12−x (MnMgTiZr) x/4 O 19 Nanoparticles

Substituted barium hexaferrite nanoparticles with composition of BaFe_12?x (MnMgTiZr) _x/4 O ₁₉ (x = 0–2.5 in a step of x = 0.5) were synthesized by co-precipitation method. The structural, magnetic, and microwave absorption properties of samples were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM), and vector network analysis (VNA). The XRD results show that the magnetoplumbite structures for all samples have been formed. The crystallite size of nanoparticles lies in the range of 26–31 nm. FE-SEM graphs indicated that the particle sizes were almost less than 100 nm and increased with an increase in Mn–Mg–Ti–Zr substitution. The result of hysteresis loops revealed that for x>1, M _s decreased with an increase in x content; furthermore, it was found that as the amount of dopant increased from x = 0 to x = 2.5, H _c decreased from 4.8 to 0.81 kOe. Based on microwave measurement on reflectivity, doped samples had much more effective reflection loss values than undoped ferrites. It was also found that the maximum reflection loss (?30.1 dB) was achieved by ferrite with the maximum amount of substitution. The obtained results reflected that the proposed composites can be introduced as electromagnetic wave absorption materials.     

Tuning of Dielectric Parameters of (NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/CuTl-1223 Nano-superconductor Composites by Temperature and Frequency

Nickel ferrite (NiFe₂O₄) nanoparticles and Cu_0.5Tl_0.5Ba₂Ca₂Cu₃O_10?δ (CuTl-1223) superconductor were prepared separately and then mixed in an appropriate ratios at the final stage to obtain (NiFe₂O₄) _x /CuTl-1223 (x = 0, 0.5, and 1.0 wt%) nano-superconductor composites. There was no significant change observed in crystal structure of the host CuTl-1223 superconducting matrix after the addition of NiFe₂O₄ nanoparticles. The value of zero-resistivity critical temperature { T _{c(R = 0)} (K)} was decreased with increasing content of these nanoparticles in these composites. Maximum values of dielectric loss tangent (tanδ) at lowest possible frequency of 40 Hz were increased with the increase of operating temperature, while its values were decreased and become almost zero at higher frequencies for all these samples at all operating temperatures. A peak in dielectric loss tangent was shifted towards lower frequency values with the addition of these nanoparticles in CuTl-1223 superconducting matrix. The dielectric loss tangent peak was also shifted towards lower frequency values in all these samples with increasing operating temperature, which shows the relaxator-like behavior in these samples. The dielectric parameters of these composites can be tuned by frequency, operating temperatures, and nature and content of these nanoparticles.     

Preparation and Magnetic Properties of La-Substituted Strontium Hexaferrite by Microwave-Assisted Sol-Gel Method

Sr_1?x La _x Fe₁₂O₁₉ (x = 0, 0.15, 0.25, 0.5) hexaferrites were prepared by microwave-assisted sol-gel method. The thermal decomposition process, structural, and magnetic properties of the products were studied by thermal differential scanning calorimeter (DSC), thermogravimetry (TG), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The phase of α-Fe₂O₃ appeared at x = 0.25 and x = 0.5. The coercivity of La³⁺-substituted strontium hexaferrites is improved to 5960.2 Oe at x = 0.25.     

Phase Distribution and Magnetic Properties of Mechanically Alloyed Hard/Soft Ferrite Nanocomposites

Improvement in the magnetic properties of hard/ soft ferrite nanocomposites was studied by varying the composition of the soft phase in SrFe₁₂O₁₉/Ni_0.5Zn_0.5Fe₂O₄ nanocomposites. The SrFe₁₂O₁₉/Ni_0.5Zn_0.5Fe₂O₄ nanocomposites were prepared using the mechanical alloying method. The samples were prepared by varying the amount of the soft phase from 10 to 50 wt% while the amount of the hard phase remained 100 wt% in the ferrite nanocomposites. X-ray diffraction (XRD), a vibrating sample magnetometer (VSM), and a transmission electron microscope (TEM) were used to characterize the samples. From the result, it was found that the nanocomposite magnet with 10 wt% of soft phase content had the highest remanence ratio, M _r / M _s , which was 0.61, while the values of the coercivity, H _c , and magnetization, M _s , measured were 4482.4 G and 9.71 emu/g, respectively, and the average particle size of the ferrite nanocomposites was < 50 nm for all the samples. It was also shown that H _c decreased as the weight percent of the soft ferrite increased, which resulted from the dipolar interaction that occurred in the ferrite nanocomposites, showing the effect of phase distribution on the magnetic properties.     

The Reflection of Cr/Fe Substitution on the Structural,Magnetic and Photoluminescence Features of Zn–Ni Based Ferrite

In this work, we substituted iron by chromium in the nano-spinel ferrite Ni_0.5Zn_0.5Fe₂O₄ (NZF), then we studied how relevant the structure, magnetic, and optical characteristics of the produced samples are changed accordingly. This doping caused a redistribution of Fe, Zn, and Ni ions over tetrahedral and octahedral sites as confirmed from XRD Reitveld analysis. Upon Cr/Fe substitution, a decrease in the lattice parameter occurred accompanied by a decrease in crystallite size of the doped samples. Magnetic measurements indicated the decrease of saturation magnetization by increasing the amount of Cr doping. On the other hand, the coercivity (H _c) increases about six times from Cr content x = 0.0 (28.28 Oe) to x = 1.0 (192.25 Oe). Photoluminescence (PL) measurements at 650 nm excitation showed emission peaks arising from Fe³⁺ transitions, band-to-band transitions, oxygen defect-related emission, and Cr³⁺ transitions that appeared strongly at heavily doped NZF with Cr. The PL intensity quenches strongly with increasing Cr/Fe ratio due to concentration, mobility, and generation of non-radiative center effects. The band gap energy of the Cr-doped NZF system is red shifted until x = 0.5 and the increases (blue shifted) at x = 0.75.     

Structural and Superconductivity Properties of BaFe<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Pt<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>As<Subscript>2</Subscript>

Extraordinary magnetic behaviors, resistivity properties, and lattice parameters of the main sample BaFe₂As₂ and BaFe_2?x Pt _x As₂ in the variation of x from 0 to 0.4 with the step of 0.1 were investigated. The bulk materials have been prepared by the solid-state reaction method and sealed into a quartz tube. The crystal structure of all samples exhibited the ThCr₂Si₂-type crystal structure which is in harmony with earlier studies in the literature. The superconducting states with magnetization measurements have been detailed in the wide temperature range 5–170 K, up to a field of 20 Oe. Increasing Pt and decreasing Fe elements in the BaFe_2?x Pt _x As₂ compound deteriorated superconductivity. Using magnetization measurement data, we present the variation of superconducting critical temperature (T _c) correlating with a Pt dopant rate from x = 0 to x = 0.4. The dopant rate of x = 0.3 exhibited the limit rate for maximum T _c; deterioration of superconductivity was revealed with a dopant rate of more than x = 0.3. This should be explained by varying T _c related to a lattice shrinking and pressure effect (geometric factor).     

Effects on dielectric and magnetic properties of Cr-doped Bi<Subscript>0.9</Subscript>Ba<Subscript>0.1</Subscript>Fe<Subscript>1−x</Subscript>Cr<Subscript>x</Subscript>O<Subscript>3</Subscript> ceramic

In this paper, Cr-doped Bi_0.9Ba_0.1Fe_1?xCr_xO₃ (x = 0.00, 0.05, 0.10, 0.15, 0.20) ceramic materials were prepared by traditional state solid synthesized method, and the effects of Cr³⁺ ion on magnetic and dielectric properties were investigated. All samples showed BiFeO₃ phase formation were successful synthesized. The SEM images showed the shape of samples changed from regular to irregular shape. With increasing of Cr²⁺ ions, Saturation magnetization (M _s) increased from 5.24 to 8.6 emu/g, and then decreased to 7.31 emu/g, and coercivity (H _c) increased from 110.66 to 256.49 Oe. All the samples showed high dielectric constants at low frequency and the values of dielectric constants decreased slightly with frequency increasing. Delectric loss (tanδ) values kept a steady in a wide range frequency of 10–600 MHz. They ranged in tanδ from 0.01 to 0.07, which was a low dielectric loss in Bi_0.9Ba_0.1Fe_1?xCr_xO₃ ceramics.     

The structure and dielectric properties of thin barium zirconate titanate films obtained by RF magnetron sputtering

Submicron thin layers of BaZr _x Ti_1–x O₃ are grown in-situ by RF magnetron sputtering of a ceramic target (x = 0.50) on a substrate of Pt/r-cut leucosapphire Al₂O₃. It is shown that the composition of the ferroelectric layer is not identical to the composition of the sputtered target and is shifted toward barium zirconate. The reasons for such behavior are discussed. The obtained samples are characterized by high breakdown voltages (1 MV/cm and higher). The structural and high-frequency dielectric properties are studied, and high tunability of the capacitance of thin layers is revealed.     

Structural,Morphological, Optical and Magnetic Properties of Al-Doped CoFe<Subscript>2</Subscript><Emphasis Type="Bold">O</Emphasis><Subscript>4</Subscript> Nanoparticles Prepared by Sol–Gel Auto-Combustion Method

CoFe_2?x Al _x O₄ (x = 0.0,0.5,1.0, and 1.5) ferrite nanoparticles have been synthesized by the sol–gel auto-combustion method. The effect of non-magnetic Al content on their structural, morphological, optical, and magnetic properties was also investigated. X-ray diffraction (XRD) diffraction analysis was applied and indicated that the synthesized nanopowders of samples with x<1.5 and calcined at 800 ^°C have single-phase spinel structure. It has shown also by increasing Al content, the particle size, lattice parameter, unit cell volume, coercivity, anisotropy constant, and magnetization decrease, while the energy band gap increases. The size of particles was measured by TEM being in the range of 65–75 nm (for x = 0.0) and 9–10 nm (for x = 1.0). For sample with x = 1.5, the minimum calcination temperature for obtaining a single-phase spinel structure was 1000 ^°C. By increasing the calcination temperature from 1000 to 1100 ^°C, the mean crystallite size and crystallinity increase, while the lattice parameter, coercivity, anisotropy constant, and magnetization decrease. The average grain size evaluated by SEM analysis was found to be \(\tilde 91\) and 166 nm for samples calcined at 1000 and 1100 ^°C, respectively.     

Influence of cerium dopant on magnetic and dielectric properties of ZnO nanoparticles

Ce-doped ZnO nanoparticles (NPs) with different Ce doping concentrations (0, 0.96, 1.96, 2.52 and 3.12 at.% of Ce) were prepared by the chemical co-precipitation method. Energy-dispersive analysis of X-rays confirms the presence of Ce in Ce-doped ZnO nanoparticles. Raman spectra revealed the hexagonal wurtzite structure of pure and Ce-doped ZnO nanoparticles and presence of various defects. The photoluminescence spectra exhibited enhanced violet and blue emission peak intensities for 0.96 at.% of Ce, while broad band green emissions decreased with Ce content. Electron paramagnetic resonance (EPR) studies revealed the presence of oxygen vacancies (V _O), zinc vacancies (V _Zn) and Ce³⁺ ions in the prepared ZnO nanoparticles. VSM studies showed room temperature ferromagnetism (RTFM) in the Ce-doped ZnO NPs. The substituted Ce³⁺ions found to induce RTFM along with V _O, V _Zn in correlation with the results obtained from the EPR, PL and Raman studies. The variation of dielectric constants (ε _r), dielectric loss (ε″) and ac conductivity (σ _ac) as a function of frequency and Ce concentration is studied using ‘Maxwell–Wagner Model.’     

Electrical and Dielectric Characterization of Bi–La Ion-Substituted Barium Hexaferrites

BaLa _x Bi _x Fe_12?2xO₁₉ (0.0 ≤ x ≤ 0.5) hexaferrites were produced by solid-state synthesis route, and the effect of Bi³⁺ and La³⁺ substitutions on electrical and dielectric properties of barium hexaferrite material were investigated. It is noticed that ac conductivity of barium (BaM) increases slightly with ionic substitutions of both La³⁺ and Bi³⁺ and then decreases. Ac conductivity is increased with increasing frequency at lower temperatures then remains constant for higher temperatures. This type of conductivity attitude could be originated from the indication of both electronics and polaron hopping mechanisms. The dielectric properties of BaLa _x Bi _x Fe_12?2xO₁₉ (0.0 ≤ x ≤ 0.5) hexaferrites represent a very interesting tunability as functions of frequency, temperature, and Bi³⁺ and La³⁺ ions.     

Microstructural and Magnetic Features of SrFe<Subscript>12</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>19</Subscript> Materials Synthesized from Different Fuels by Sol-Gel Auto-Combustion Method

The nanocrystalline SrFe₁₂ O ₁₉ materials were prepared by a sol-gel auto-combustion method using different fuels such as citric acid, dextrose, aniline, and hexamine. The combustion product obtained from all the fuels except from that of aniline show a single phase of SrFe₁₂ O ₁₉ materials upon annealing at 1000 ^°C/2 h. The combustion product obtained from aniline as fuel shows SrFe₁₂ O ₁₉ as the main phase with α-Fe₂ O ₃ as impurity. No notable change in lattice parameters is observed due to variation in fuels for SrFe₁₂ O ₁₉ materials. With a little change in the NIR relative reflectance (72–85 %) on fuels, the different SrFe₁₂ O ₁₉ materials display high NIR reflectance in the wavelength range, 1500–2500 nm. The photoluminescence emission spectra of SrFe₁₂ O ₁₉ materials reveal a broad emission peak at ～350 nm which is reminiscent to the Ba-based hexaferrite, BaFe₁₂ O ₁₉. The FESEM images expose quite dissimilar morphology for the various fuels used in the synthesis of SrFe₁₂ O ₁₉ materials. Hysteresis loops for all the nanocrystalline SrFe₁₂ O ₁₉ materials observed under the applied field of ±1.5 T at room temperature exhibit hard ferromagnetic property. The SrFe₁₂ O ₁₉ materials produced from glycine and aniline as fuels exhibit highest and lowest M _s values of 61.3 and 50.5 emu/g, respectively.     

Tunable Microwave Absorption Properties in Ni–Zn-Substituted BaCoTiFe<Subscript>10</Subscript>O<Subscript>19</Subscript>

Ni–Zn-substituted BaCoTiFe₁₀O₁₉ were successfully prepared by a sol-gel combustion method. The grain size of samples is about 150–800 nm ,and the grains first increase and then decrease with increasing x. Through XRD analysis, all diffraction peaks correspond to the BaTiCoFe₁₀O₁₉ and no other phase signal is detected. With x = 0.3, the saturation magnetization (M _s) is biggest (66.7 emu/g) and its coercivity (H _c) is 172.3 Oe. The curves μ ^″ ? μ ^′ have distorted semicircles, and each semicircle has an extremum. Each extremum of μ ^″ ? μ ^′ curve corresponds to a peak of μ ^″ curve and has response to reflection loss (RL), which is further illuminated. When x = 0.3, the widest bandwidth of R L ≤?10 dB is 6.13 GHz (9.68–15.81 GHz) at d = 2.6 mm. The RL curve closely relates to distorted semicircle of μ ^″ ? μ ^′ curve, and the relation is also deeply illuminated, which is beneficial to study absorption materials.     

Influence of cerium substitution on structural,magnetic and dielectric properties of nanocrystalline Ni–Zn ferrites synthesized by combustion method

Nickel–Zinc (Ni–Zn) ferrites substituted by cerium (Ce) and having the chemical composition Ni_0.5Zn_0.5Ce _x Fe_2?x O₄ (x?=?0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were synthesized by combustion method using the organic fuel urea as reducing agent. The effects of cerium substitution on the structural, magnetic and dielectric properties of Ni–Zn compounds have been evaluated. X-ray diffraction patterns indicate that the Ni_0.5Zn_0.5Ce _x Fe_2?x O₄ crystallizes into cubic spinel structure initially and secondary phase emerged along with main spinel phase when the Ce³⁺ content is increased. The elemental composition analysis confirms the stoichiometric presence of expected elements in the samples. Scanning electron microscope and high-resolution transmission electron microscope images reveal the nature of grain growth and the particle size of the synthesized samples. Fourier transform infrared spectroscopy confirms the formation of spinel phase and predicted the shifting of bands corresponding to Fe–O vibrations towards higher wavenumbers compared to undoped Ni–Zn ferrite. Magnetic characterization studies reveal that the substitution of Ce³⁺ into the Ni–Zn ferrite leads to a significant change in saturation magnetization and coercivity values. A plot of dielectric constant (?′) versus applied electrical frequency measured at room temperature shows the normal dielectric behavior of the spinel ferrites. The introduction of Ce³⁺ rare earth ions into Ni–Zn ferrites samples is found to affect the values of both dielectric constant and AC conductivity.     

Fabrication,Characterization, and Magnetic Properties of BaAlFe<Subscript>11</Subscript>O<Subscript>19</Subscript> Particles Via Auto Combustion Method

Al-substituted barium hexaferrite particles have been successfully synthesized via sol-gel auto combustion method in the presence of citric acid as fuel. Thermal decomposition, phase evolution, and the microstructure of products were characterized by DTA/TG, XRD, and SEM. Magnetic measurements were carried out on a VSM. To investigate the effects of citric acid to metal nitrate (CA/MN) molar ratios and combustion temperatures on the morphology, phase structure, and magnetic properties of products and finding the optimal condition, several experiments were carried out. The results revealed that the formation temperature, crystallite size as well as magnetic properties are significantly influenced by these parameters. A saturation magnetization of 56.96 emu/g and a coercivity of 7279 Oe were obtained in BaAlFe₁₁O₁₉ powders with CA/MN = 1.0. High Ms and Hc values make them particularly suitable for hard magnetic applications.