BiFeO3 Powders Research Articles

Structures, dielectric properties and AC impedance characteristics of BiFeO3–BaTiO3 high-temperature lead-free piezoceramics synthesized by the hydrothermal method

Among the lead-free piezoceramics, ([Formula: see text])BiFeO[Formula: see text]BaTiO3 (BF-BT) is considered a promising candidate for high-temperature piezoelectric materials owing to its high Curie temperature ([Formula: see text]C) and good electromechanical properties. In this work, the hydrothermal synthesis method was used to prepare the precursor powders of BiFeO3 and BaTiO3, and then the mixed powder compacts with the chemical composition of 0.7BF–0.3BT were sintered under pressureless conditions. The influence of the hydrothermal reaction times (12–24[Formula: see text]h) of BiFeO3 on the structures and electric properties of the sintered ceramics was instigated. First, all the samples synthesized with the tetragonal BaTiO3 and BiFeO3 powders were identified with relatively stable dielectric properties. As the hydrothermal reaction time to synthesize BiFeO3 increased, the dielectric properties as well as the temperature stability of the 0.7BiFeO3–0.3BaTiO3 ceramics also improved. At the condition of a hydrothermal reaction time of 24[Formula: see text]h, the sample obtained possesses both the lowest temperature coefficient of dielectric constant ([Formula: see text]C between RT and [Formula: see text]C) and the highest Curie temperature ([Formula: see text]C at 100[Formula: see text]kHz). Moreover, at high temperatures, it exhibits a higher AC impedance than others. The calculating result based on the resistive constant-phase-element model (R-CPE) circuit model showed that the grain boundary of the 0.7BF–0.3BT ceramics contributes more resistance to the conductivity at high temperatures. In summary, the hydrothermal reaction proved to be a useful way that achieves the preparation of single-phase 0.7BF–0.3BT ceramics with improved electrical properties.

Photocatalytic properties of BiFeO3 powders synthesized by the mixture of CTAB and Glycine

Highly pure BiFeO3 (BFO) powders were prepared by the solution combustion synthesis method using cetyltrimethylammonium bromide (CTAB) and glycine as fuels at various fuel-to-oxidant (φ) ratios. Microstructural characteristics, morphology, optical properties, and thermal analysis were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and differential thermal/thermogravimetry (DTA/TGA), respectively. The combusted powders prepared at different fuel content contained a small amount of impurity phases such as Bi24Fe2O39 and Bi2Fe4O9. During the calcination of BFO powders at 600 °C for 1 h, a nearly pure BFO phase was produced. Combusted powders photodegraded about 80% of methylene blue dye at φ = 2 through 90 min of visible light irradiation.

Comparative studies of La and Co modified BiFeO3 (0.05) prepared by sol–gel versus conventional solid state reaction method

In this article, we looked at how the multifunctional characteristics of a multiferroic BiFeO3 were affected by the synthesis process. La and Co modified BiFeO3 powders with x= 0.05 were prepared by conventional solid-state reaction and sol–gel route. The X-ray Diffraction patterns of both the samples, prepared by sol–gel and solid-state route show single-phase formation. It has been observed that sol–gel route attains the low temperature phase formation as compared to the solid state route. The density was optimized by sintering these samples at different loads. Room temperature dielectric plots with the frequency of these samples revealed that the dielectric constant decreases with frequency, and dielectric loss in the solid state reaction (SSR) prepared sample is smaller than the sol–gel route (SGR) prepared sample. The effects of processing on dielectric properties of La and Co modified BiFeO3 have been studied in the different frequency and temperature range from 300 K (RT) to 550 K. Dielectric anomalies in temperature dependent dielectric plots have been observed in both of the samples.

Multiferroics Made via Chemical Co-Precipitation That Is Synthesized and Characterized as Bi(1−x)CdxFeO3

Cd-doped BiFeO3 powders, with varying doping concentrations of Cd (Bi(1−x)CdxFeO3, where x = 0–0.3), were prepared through a facile chemical co-precipitation method and calcinated at 550 °C in the air. The BiFeO3 has a rhombohedral crystal structure, which changes to an orthorhombic crystal structure with an increase in Cd doping. The presence of dopant has also altered the bandgap of material suppressing it from 2.95 eV to 2.51 eV, improving the visible light absorption. Vibrating sample magnetometry (VSM) confirmed stronger ferromagnetic character for Bi0.7Cd0.3FeO3 with a coercivity of 250 Oe, and remnant magnetization was 0.15 emu/g, which is because of the misalignment of the two sublattices of perovskite structure after doping resulting in the imbalanced magnetic moment giving rise to net nonzero magnetic behavior. The particle size reduction is observed with an increase in the doping concentration of Cd.

On the enhanced dielectric and magnetic properties of BiFeO3 ceramics sintered under meta-stable conditions

Multiferroic BiFeO3 (BFO) ceramics are synthesized by non-thermodynamically stable methods, such as fast firing, cryomilling and Spark Plasma Sintering (SPS) with applied pressure of 60 MPa and high heating rate of 150 K/min. We obtained BFO ceramics and powders that present enhanced magnetic and electrical properties. The observed enhancements are caused by the chosen routes, such as cryomilling, which causes a significant reduction of crystallite size, reaching 23 nm, and a high micro-strain level, reaching 1.2%. This is reflected in the magnetic curve which is changed from antiferromagnetic-like to weak-ferromagnetic-like, with an increased maximum magnetization from 0.085 emu/g to 0.369 emu/g. The dielectric constant reached a high value, close to Ɛ’= 102 coupled with low dielectric loss (tan δ ∼ 0.019) over a wide range of frequencies (1 kHz to 2 MHz), reaching values close to 0.005 near 2 MHz. Such dielectric constant (dielectric loss) values are generally present for highly resistive ceramics. By equivalent circuit fitting we managed to separate the grain and grain boundary contributions. These results and those from XRD diffraction and Mössbauer spectroscopy indicate a migration of defects to the surface of the grains. In summary, we managed to consolidate this sintering method as a powerful method to obtain BFO ceramics with enhanced electrical and magnetic properties. Such improvements, especially the high resistivity and low tangent losses, can open new avenues for future technological applications of BiFeO3 nanostructured ceramics, such as ferroelectric memories and the magnetic enhancements for spintronic based devices.

Fine Control of Multiferroic Features of Nanoscale BiFeO3 Powders Synthesized by Microwave-Assisted Solid-State Reaction

Fine Control of Multiferroic Features of Nanoscale BiFeO3 Powders Synthesized by Microwave-Assisted Solid-State Reaction

Low Temperature Magnetic Transition of BiFeO3 Ceramics Sintered by Electric Field-Assisted Methods: Flash and Spark Plasma Sintering

Low temperature magnetic properties of BiFeO3 powders sintered by flash and spark plasma sintering were studied. An anomaly observed in the magnetic measurements at 250 K proves the clear existence of a phase transition. This transformation, which becomes less well-defined as the grain sizes are reduced to nanometer scale, was described with regard to a magneto-elastic coupling. Furthermore, the samples exhibited enhanced ferromagnetic properties as compared with those of a pellet prepared by the conventional solid-state technique, with both a higher coercivity field and remnant magnetization, reaching a maximum value of 1.17 kOe and 8.5 10-3 emu/g, respectively, for the specimen sintered by flash sintering, which possesses the smallest grains. The specimens also show more significant exchange bias, from 22 to 177 Oe for the specimen prepared by the solid-state method and flash sintering technique, respectively. The observed increase in this parameter is explained in terms of a stronger exchange interaction between ferromagnetic and antiferromagnetic grains in the case of the pellet sintered by flash sintering.

Facile and highly efficient wet synthesis of nanocrystalline BiFeO3particles by reverse co-precipitation method

In this study a nanocrystalline bismuth ferrite BiFeO3 (BFO) powder was synthesized using a novel, facile and highly efficient reverse co-precipitation method. Proposed method is also highly cost-efficient and environmentally friendly. It was demonstrated that the optimal calcination temperature for the preparation of phase-pure BFO is 400 °C, while at higher temperatures formation of undesirable crystal phases occur. X-Ray diffraction studies were employed for the investigation of crystal structure and phase composition of obtained powders. Scanning electron microscopy (SEM) was used to evaluate the morphology of synthesized powders. For piezoelectric studies, precursors powders were pressed into 12.5 mm diameter pellets and calcined at the same temperatures. Obtained materials show very good piezoelectric properties, as a result of high defects homogeneity and very low crystallite size. Determined piezoelectric coefficient is comparable with praseodymium, samarium or europium doped BiFeO3 ceramic.

Enhanced Photocatalytic Activities for Degradation of Dyes and Drugs by Crystalline Bismuth Ferrite-Modified Graphene Hybrid Aerogel

Industrial wastewater contains diverse toxic dyes and drugs, which pollute the environment and poison creatures. Utilizing photocatalysts has been accepted to be an effective method to degrade water pollutions using solar light. Crystalline bismuth ferrite (Bi2Fe4O9) with a band gap of 1.9–2.0 eV is expected to be one of the most promising candidates for photocatalysts in the visible light region. Amorphous graphene is also a promising candidate as a photocatalyst owing to its excellent electronic and optical properties. Herein, a composite of Bi2Fe4O9/graphene aerogels (GAs) was prepared with a two-step hydrothermal method. The prepared Bi2Fe4O9 powders were confirmed to be successfully doped into GAs and evenly dispersed between graphene sheets. The Bi2Fe4O9/GA composite was utilized to perform photodegradation for organic dyes and antibiotic drugs under visible light irradiation, yielding efficiencies of 90.22%, 92.3%, 71.8% and 78.58% within 330 min for methyl orange, methylene blue, Rhodamine B and tetracycline hydrochloride, respectively. Such distinct photocatalytic activities overwhelmed the pure Bi2Fe4O9 powders of 14.10%, 22.19%, 13.98% and 48.08%, respectively. Additionally, the composite produced a degradation rate constant of 0.00623 min−1 for methylene blue, which is significantly faster than that of 0.00073 min−1 obtained by the pure powder. These results provide an innovative strategy for designing 3D visible-light-responsive photocatalysts combined with graphene aerogel for water purification.

Study of the optical properties of BiFeO3 under different heat treatment temperatures

It is known that the optical absorption property of a material is linked to its crystal structure. Therefore, it can be modified or displaced when the material is subjected to thermal treatments, generating displacements of the unit cell, atomic positions and bond angles of its atoms. In this work, the analysis of three samples of BiFeO3 powders subjected to different heat treatment temperatures was carried out to study their optical properties by analyzing the crystal structure, diffuse reflectance, Raman scattering spectroscopy, density of state and band structure. In the results, the pure phase and the hexagonal structure of the samples were identified, showing an increase in the angles between the Fe-O-Fe atoms when the material is thermally treated. The band gap (Egexperimental) of the BiFeO3 samples without and with treatment temperature showed direct and indirect transitions according to the Tauc equation, these values were 2.36, 2.11 and 2.19 eV for direct band gaps and 2.10, 1.58 and 1.85 eV for indirect band gaps. In the Raman scattering spectroscopy analysis, overtones were observed in the samples when a green laser with a wavelength of 532nm (2.33 eV) was applied. In the density of states, the maximum valence band formed by the O(2p) state and the minimum of the conduction band formed by the hybridization of the Fe(3d) and O(2p) states were identified. In the electronic band structure, indirect band gap values (Egtheoretical) of 2.274, 2.216 (500 °C) and 2.217 eV (600 °C) were found for the samples without and with heat treatment. It is concluded that BiFeO3 absorbs visible light and that its band gap can decrease by increasing the bond angle of Fe-O-Fe atoms when the sample is subjected to heat treatment. These results demonstrate the semiconductor property of BiFeO3 and can be applied to solar cells, batteries, hydrogen production, among other applications.

Chelating Agents Assisted Rapid Synthesis of High Purity BiFeO3: Remarkable Optical, Electrical, and Magnetic Characteristics

In this study, we presented two reliable methods, the sol–gel and autocombustion, to synthesis a high purity BiFeO3 single phase with low calcination time using glycine as chelating agent. The glycine-autocombustion method produced a high purity BiFeO3 phase using either low or high concentrations of the reactants (Bi(NO3)3 + Fe(NO3)3), while the glycine-sol–gel method delivered a high purity BiFeO3 phase using low concentrations of reactants. In the case of using tartaric acid and urea as chelating agents, mixtures of BiFeO3 and Bi25FeO40 phases were formed. The morphology, size, and porosity of the particles were obviously changed by varying the synthesis method and chelating agents. The high purity BiFeO3 samples exhibit a visible light band gap of 2.05 eV with long absorption tail extending to the infrared region, suggesting the suitability of the synthesized powders in the solar photocatalytic applications. A weak hysteresis ferromagnetic loop was observed for BiFeO3 (glycine method) and BiFeO3/Bi25FeO40 (urea method) with large contribution from the paramagnetic behavior. On contrast, robust ferromagnetic loops were found for BiFeO3/Bi25FeO40 sample synthesized by tartaric acid with saturation magnetization reaching to 2.5 emu/g. Remarkably, the pure single phase BiFeO3 powders synthesized by sol–gel and auto-combustion methods using glycine possess room temperature dielectric constant values of 622 and 845 respectively at a frequency of 42 Hz. In the case of BiFeO3 powders prepared by using tartaric acid, the dielectric constant exhibits values of 401 and 1118 for sol–gel and auto-combustion assisted samples, at the same frequency, respectively. At low frequency, the values of the real part of the complex permittivity tend to be zero which confirms a negligibly small contribution of the electrode effect.

Structural, dielectric, magnetic, and ferroelectric properties of bismuth ferrite (BiFeO3) synthesized by a solvothermal process using hexamethylenetetramine (HMTA) as precipitating agent

Multiferroic BiFeO3 (BFO) has been synthesized by the solvothermal technique for 4 h at 180 °C using Hexamethylenetetramine (HMTA) as a precipitating agent. Optimizations on HMTA concentration were performed to attain BFO in a narrow possible time using the solvothermal method. The effect of HMTA concentration on structural properties was investigated by XRD, FE-SEM, FT-IR, and Raman techniques. Moreover, the magnetic, ferroelectric, dielectric, and optical properties were studied by VSM, Ferroelectric analyser, Dielectric spectrometer, and UV–Vis–NIR spectrometer, respectively. The XRD data has unveiled the significant role of HMTA, as a precipitating agent, in obtaining the pure phase BFO at a particular concentration. A high concentration of HMTA (6 M) is found to be more favourable for producing pure phase BFO within the short reaction time of 4 h without any impurity phase formations. The FE-SEM images have shown the formation of granular structures that are inhomogeneously distributed throughout the powdered BFO with porosities. In addition, the magnetic measurements confirmed that the BFO synthesized with varying HMTA concentration exhibits a reasonable week ferromagnetic behaviour. However, the pure BFO powder synthesized at 6 M HMTA shows high magnetization value (0.72 emu/g) compared to the other samples synthesized at low concentrations of HMTA. Further, the dielectric measurements of all the synthesized BFO samples have shown a decrease in dielectric loss with an increase in frequency. Whereas the dielectric behaviour exhibited by the pure BFO synthesized at 6 M HMTA has shown a high dielectric constant value with moderate dielectric loss. A ferroelectric analyser studies the ferroelectric behaviour of BFO powder. The study revealed that pure phase BFO synthesized with 6 M HMTA exhibits a high value of remanent polarization with unsaturated P-E loops due to the high leakage current in the sample. The UV–Vis data shows that the BFO samples exhibited an excellent optical absorption in the visible range with narrow optical band gaps. Therefore, all the characterizations related to magnetic, structural, dielectric, ferroelectric, and optical properties of synthesized pure BFO have proven the significance of precipitating agent HMTA in the solvothermal synthesis method. Based on our findings, the synthesized pure phase BFO can be an excellent semiconducting photocatalyst for multiferroic based photocatalysis applications.

Effect of Cobalt Substitution on the Structural and Magnetic Properties of Bismuth Ferrite Powders

BiFeO3 (BFO) is a multiferroic material with excellent ferroelectric properties but with poor magnetic behavior. Therefore, we focused principally on the enhancement of the magnetic order of BFO. These multiferroic properties make BFO an excellent candidate for magnetoelectric devices at room temperature. Pure and Co-BiFeO3 powders were successfully synthesized via the sol–gel method at 700 °C. The effect of Co substitution on the corresponding structural and magnetic properties of BFO was studied. X-ray diffraction and Fourier Transform Infrared Spectroscopy measurements confirmed the rhombohedral perovskite structure in all samples. A secondary phase of CoFe2O4 (CFO) was detected for 9, 10, and 15% of Co doping. The scanning electron microscopy images of the Co-BFO particles showed a reduction in the particle size compared to the pure BFO powders. Vibrating sample magnetometry measurements evidenced the ferromagnetic hysteresis loop for the Co-BFO powders with values of saturation magnetization of 4.1 emu/g and a coercivity of 1083 Oe for 15% of Co doping. In this work, we report impurity free samples with notable magnetic properties at the same time, which is a difficult challenge in bismuth ferrite synthesis. This is the first step for later applications in future technology.

Auto-combustion synthesis as a method for preparing BiFeO3 powders and flexible BiFeO3/PVDF films with improved magnetic properties. Influence of doping ion position, size and valence on electric properties

Bismuth ferrite (BiFeO3) powders were synthesized by auto-combustion method using glycine as a fuel. Doping ions of different valence were used to study the influence on electrical conductivity and ferroelectric properties. Powders were mixed and hot-pressed with α-PVDF to form flexible composite samples. Composites endured significantly higher electrical fields with lower leakage and retained the weak ferromagnetism present in powders. Dielectric properties were improved by doping with Zr4+, Y3+ and Ca2+ as well as the electrical resistivity. Flexible composites exhibited improved electrical resistivity and modified conduction mechanism. Relatively high magnetization of powders completely originates from magnetite particles formed during the combustion, while sintered samples exhibited typical antiferromagnetic behaviour.

Analysis of the effect of cationic ratio Bi3+/Fe3+ on the magnetic and multiferroic properties of BiFeO3 nanoparticles synthesized using a sonochemical-assisted method

This study examined the effects of the cationic ratio of Bi3+/Fe3+ via X-ray photoelectron spectroscopy (XPS) on the magnetic and multiferroic properties of BiFeO3 nanoparticles synthesized using a sonochemical-assisted method. X-ray diffraction revealed the successful synthesis of single-phase BiFeO3 powder after annealing the sonicated material at 723 K. The powder was composed of agglomerates of rounded particles with a mean particle size of 35 nm. XPS was performed to determine the Bi3+/Fe3+ ratio as a function of the heat treatment process and its relationship with secondary phases, which can modulate the magnetic properties of the nanopowders. The cationic ratio obtained by XPS confirmed that the powders obtained at 623 and 923 K have excess Bi3+ and Fe3+, respectively, which induces the formation of Bi24Fe2O39 and Bi2Fe4O9 as the majority phases. Powder annealing at 723 K revealed a ferromagnetic order with specific magnetization of 1.8 Am2/kg. This ferromagnetic behavior was preserved after applying spark plasma sintering (SPS) at 923 K. By contrast, conventional sintering at 1023 K promotes antiferromagnetic order. In addition, the dielectric properties of the ceramic material of the sintered powders showed a behavior related to a typical ferroelectric material.

Synthesis and Investigation of Structural and Magnetic Properties of Nickel Doped BiFeO3

Ni doped BiFeO3 powders were synthesized by sol-gel method. The effect of annealing temperature and solvent type on the structural and magnetic properties of the synthesized powders has been studied by XRD, SEM, EDX, VSM and FMR techniques at the room temperature. XRD results highlighted that the Ni doped BiFeO3 powders were successfully synthesized. The morphology changes with annealing temperature and solvent material. With EDX analysis, all the elements in Ni doped BiFeO3 powders were confirmed. The magnetic properties of the samples were observed to strongly depend on annealing temperature and solvent material. The saturation magnetization is observed to increase with an increasing annealing temperature. The broad resonance lines indicate ferromagnetic property.

The Influence of Annealing Temperature on the Structure and Magnetic Properties of Nanocrystalline BiFeO3 Prepared by Sol\u2013Gel Method

In this work, BiFeO3 powders were synthesized by a sol–gel method. The influence of annealing temperature on the structure and magnetic properties of the samples has been discussed. X-ray diffraction studies showed that the purest phase was formed in the temperature range of 400 °C to 550 °C and the samples annealed at a temperature below 550 °C were of nanocrystalline character. Mössbauer spectroscopy and magnetization measurements were used as complementary methods to investigate the magnetic state of the samples. In particular, the appearance of weak ferromagnetic properties, significant growth of magnetization, and spin-glass-like behavior were observed along with the drop of average grain size. Mössbauer spectra were fitted by the model assuming cycloidal modulation of spins arrangement and properties of the spin cycloid were determined and analyzed. Most importantly, it was proved that the spin cycloid does not disappear even in the case of the samples with a particle size well below the cycloid modulation period λ = 62 nm. Furthermore, the cycloid becomes more anharmonic as the grain size decreases. The possible origination of weak ferromagnetism of the nanocrystalline samples has also been discussed.

Enhanced magnetoelectric coupling response in hot pressed BiFeO3 and polymer composite films: Effect of magnetic field on grain boundary and grain resistance

We report the effect of grain boundary resistance (GBR) and grain resistance (GR) on the magnetoelectric coupling in the multiferroic composite thick films of BiFeO3 (BFO) nanocrystalline powder and poly vinylidene-fluoride (PVDF) polymer. These composite thick films of thickness ∼ 0.2 mm were prepared via hot pressing with the weight ratio of BFO powder and PVDF polymer as 70:30 (abbreviated as BFO70), 60:40 (abbreviated as BFO60), 50:50 (abbreviated as BFO50) and 40:60 (abbreviated as BFO40), respectively. Impendence investigations (Cole-Cole plots) of these thick films demonstrate that the GBR is significantly changed on the application of magnetic field (8 kOe) in comparison to the GR. Our results indicate that the GBR plays an important role in strengthening of magnetoelectric (ME) effect in BFO-PVDF system. In addition, the ME coupling study indicates that the BFO50 sample shows better results (α33 ∼ 2.7 mV/cm-Oe) and may be suitable for device and sensor applications.

Controlled preparation of magnetically separable BiOBr/BiFeO3 heterostructures by chemical etching process with enhanced visible light photocatalytic activities and anti-photocorrosion

ABSTRACT Novel magnetically separable BiOBr/BiFeO3 heterostructures were fabricated via a facile in situ hydrothermal chemical etching process using cetyltrimethyl-ammonium bromide (CTAB) and sulphuric acid as etching agents to react with BiFeO3 particles. The effects of solution pH and CTAB amount on the structure, morphology, and optical properties of the as-prepared samples were investigated. It was found that the best acidity of solution is pH = 3.0 for the formation of BiOBr/BiFeO3 heterostructures from BiFeO3 powder. Their photocatalytic activities and anti-photocorrosion behaviour were measured by the photocatalytical reduction of heavy metal ion Cr (VI) under visible-light irradiation. Experimental results show that the molar ratio of BiOBr to BiFeO3 contributed to different morphologies and photocatalytic activities of BiOBr/BiFeO3 composites. The optimised molar ratio in BiOBr/BiFeO3 composites was found to be 1:1. The photocatalytic reduction rate of Cr(VI) over 1:1 BiOBr/BiFeO3 composites was found to be 4.9 and 3.0 times higher than that of pure BiFeO3 and BiOBr, respectively. The hybridisation of BiOBr with BiFeO3 can markedly inhibit the photocorrosion of semiconductor BiFeO3. No obvious catalytic activity decrement can be found after five consecutive photocatalytic Cr (VI) reduction, which demonstrates the high structural stability of 1:1 BiOBr/BiFeO3. Furthermore, a possible photogenerated charge transfer process was proposed. The obviously enhanced photocatalytic activity could be ascribed to the formation of BiOBr-BiFeO3 heterojunction, accelerating the effective separation of photoexcited electron−hole pairs. This study suggests that the magnetically separable BiOBr/BiFeO3 heterostructures can be a promising photocatalyst for environment-related applications.

Synthesis of Bismuth Ferrite and its Application for Oscillator Material up to 25 GHz Range

Among other multiferroic materials, bismuth ferrite (BiFeO3) attracts much attention due to its room-temperature properties and its wide potential applications. However, the synthesis to obtain a single-phase material is hard to be achieved because of the volatility of bismuth oxide. In this study, the BiFeO3 powders were synthesized by using a sol-gel method from the nitrates of bismuth and iron salt with the various stoichiometric ratios between Bi and Fe of 1:1.02, 1:1, 1.02:1, and 1.03:1. The single-phase and a good stoichiometric ratio of Bi: Fe = 1:1 was obtained from the starting composition ratio of 1.03:1 with a quenching process from 550°C sintering temperature. The single-phase of BiFeO3 shows a hysteresis curve of a weak antiferromagnetic with a coercive field of about 1.38 kOe at room temperature. The measurement of microwave oscillator was measured by using a dielectric resonator from 0 to 25 GHz does not show any resonant peak.