Remanence Values Research Articles

Magnetic and optical characterizations of Dy-Eu co-substituted Mn0.5Zn0.5Fe2O4 nanospinel ferrites

In this study, Mn0.5Zn0.5DyxEuxFe2–2xO4 (x ≤ 0.1) nanospinel ferrites (DyEu→MnZn (x ≤ 0.1) NSFs) were synthesized via ultrasonication method. The microstructure of samples was characterized by XRD, which confirmed the cubic spinel phase without any impurity and the nanostructure of all samples. TEM and SEM also proved the samples' morphology and chemical composition along with EDX. Diffuse reflectance (DR) spectra investigations were performed on samples. Direct optical energy band gaps (Eg) were studied by using the Tauc approximation and were found between 2.44 and 2.56 eV. The impact of Eu3+-Dy3+ ions inclusion on the magnetic properties of DyEu→MnZn (x ≤ 0.1) NSFs was also investigated. The magnetic M-H hysteresis loops showed non-hysteretic behavior at 300 K, suggesting the superparamagnetic (SPM) behavior. In contrast, finite values of coercivity and remanence are observed at lower temperatures (T) (10 K), revealing the transition to ferromagnetic (FM) behavior at low Ts. As the concentration of Eu3+-Dy3+ ions increases, it is noticed that the saturation magnetization (Ms) decreases, whereas the coercivity (Hc) increases. The curves of T-dependent magnetization M(T) under FC and ZFC modes confirmed the SPM-FM phase transition with decreasing the T. It is found that the blocking temperature (TB) is slightly decreasing with increasing the Eu3+-Dy3+ ions content. All samples displayed spin-glass-like behavior at low Ts, which indicates strong interactions among the magnetic moments.

Superparamagnetic-like Micrometric Single Crystalline Magnetite for Biomedical Application Synthesis and Characterization

Single-crystalline magnetite (Fe3O4) particles having a size beyond the nanometric range (1 µm to 50 µm) and showing high (close to the bulk value) saturation-specific magnetization (σs = 92 emu/g), were obtained by the hydrothermal decomposition of the Fe-EDTA complex. The very low values of the magnetic remanence (σr = 0.82 emu/g) and coercitivity (μoHc = 1.53 mT) observed at room temperature (RT) suggest a superparamagnetic-like behavior, which is quite remarkable for such micrometric magnetite particles. As confirmed by vibrating sample magnetometer (VSM)-based measurements, minor changes in their magnetic properties occur between RT and 5K. Scanning electron microscopy (SEM) has revealed a morphology consisting of a combination of non-porous octahedral- and dodecahedral-shaped particles, energy dispersive X-ray analysis (EDX) has indicated high elemental (Fe and O) purity, whereas X-ray diffraction (XRD) has confirmed a single crystal structure. The nitrogen adsorbtion–desorption isotherm and pore size distribution are presented for the magnetite sample. Thermomagnetic records under zero field-cooled (ZFC) and field-cooled (FC) conditions have revealed a thermal hysteresis of the Verwey transition.The Verwey point (TV) at which the major step of the phase transformation takes place is located around 132 K for heating and around 122 K for cooling. These microcrystals do not remain agglomerated when the polarizing field is removed, an essential requirement in biomedical applications is met.

A novel metallurgical technique for the preparation of soft magnetic iron carbide from low-grade siderite

Iron carbide (Fe3C) has attracted widespread attention as a functional material, catalyst, and magnetic material. In this study, soft magnetic Fe3C was prepared by carburization roasting, magnetic separation, and acid leaching using low-grade siderite as the raw material. The effects of carburization, subsequent magnetic separation, and acid leaching of the carburized samples on their magnetic properties were studied using a vibrating sample magnetometer (VSM), and the mechanisms of these methods were also studied. The final samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), VSM, and Mössbauer spectroscopy. Under optimized conditions, an iron carbide material comprising assaying 92.08% Fe and 6.94% C with a corresponding iron recovery rate of 73.50% was obtained. The saturation magnetization, the remanence, and coercivity values of the obtained iron carbide were 136.10 emu/g, 1.84 emu/g, and 39.11 Oe, respectively. Furthermore, Na2SO4 and NaOH were found to be useful additives for improving the carburization efficiency of iron carbide, enlarging iron carbide particles, improving the embedding relationship between iron carbide and gangue, and enhancing the dissolution of gangue in acid. The proposed technique is promising for the preparation of magnetic iron carbide materials with good soft magnetic performance.

Silica supported spinel structured cobalt ferrite multifunctional nanocatalyst for hydration of nitriles and oxidative decarboxylation of phenylacetic acids

The silica‐supported cobalt ferrite spinel nanocatalyst has been successfully synthesized by the coprecipitation method and extensively characterized by FTIR, XRD, SEM‐EDX, TEM, BET, VSM, XPS, TGA, and ICP‐AES analysis. The bands observed at 3435 cm−1(νOHof Si‐OH) and 1637 cm−1(γOHof Si‐OH) in the FTIR spectrum of the as‐synthesized nanocatalyst unambiguously tell the presence of silica support. Moreover, a very weak intensity and a medium intensity peak at 683 cm−1and 463 cm−1suggested intrinsic stretching vibrations of Fe‐O and Co‐O of cobalt ferrite, respectively. The XRD pattern confirms the formation of CoFe2O4spinel. The average crystallite size was found to be 5.4 nm as calculated by using the Debye–Scherrer equation based on the (220) plane while the average particle size was found to be 5.08 nm from TEM analysis. The crystalline nature of the nanocomposite was confirmed by the SAED pattern. The successful incorporation of CoFe2O4on the surface of silica was established by the BET surface area measurements. The silica‐supported cobalt ferrite nanocatalyst has been explored as a heterogeneous multifunctional catalyst for hydration of nitriles and oxidative decarboxylation of phenylacetic acids as well under mild reaction conditions with moderate to excellent isolated yield of the desired products (60–99%). The catalyst was magnetically recoverable within a time frame of ~90 s and reusable up to the fifth catalytic cycle without profound loss of activity. A magnetic hysteresis study was performed to elucidate the magnetic behavior of the catalyst. The saturation magnetization value of 39.785 emu/g with a coercivity value of 110.87 Oe and saturation remanence value of 5.185 emu/g clearly indicated the presence of a ferromagnetic component in the material.

Unveiling the effect of annealing on magnetic properties of nanocrystalline half-metallic Heusler Co2FeSi alloy glass-coated microwires

In this article, we present a new Co2FeSi glass-coated microwire obtained by Taylor-Ulitovsky technique with nanocrystalline structure consisting of a mixture of bcc phase (lattice parameter, a = 5.640 Å, crystalline grain size, Dg = 17.8 nm) in as-prepared sample. The annealing temperature was fixed at 873 K, and the annealing time was 1 and 6 h. The annealing resulted in a significant increase of such nano-grains up to (31.6 nm). Perfect square hysteresis loops have been observed in all annealed samples at a wide temperature range (55–400 K) that are not seen in the as prepared sample. The thermal magnetic behavior for the annealed samples shows dramatic magnetic behavior at low temperature. Large irreversibility magnetic behavior with a blocking temperature (Tb = 150 K) has been observed for annealed sample for 1 h. Critical temperatures of 155 K and 105 K have been detected for annealed samples for 1 h and 6 h, respectively, where the behavior of M−H loops, coercivity and remanence changed. Below the critical point the M−H shows wasp-waisted, multistep magnetic behavior and complex magnetic reversal mechanism is supposed. The anomalous magnetic behavior is due to the coexistence of the ordered and disordered phases induced by annealing conditions below the room temperature. The difference in the magnetization behaviour, remanence, and coercivity values for Co2FeSi glass-coated microwires samples indicates the influence of internal stresses created by the presence of the glass coating. These finding opens the door to design spintronic devices based on the magnetization switching.

Morphology, structural, dielectric and magnetic study of Ce3+ ion doped Mg0.5Zn0.5Fe2-xCexO4 (0.0≤x≤0.1) ferrite nanoparticles

The current work involves the co-precipitation process to synthesize Ce3+ ion doped MZP ferrite nanoparticles. The single-phase spinel structure of all the samples is confirmed by XRD. As per the Debye-Scherrer formula, the nanoparticles crystallite size is in the range of 7–12 nm. The emergence of 450 cm−1 and 560 cm−1 distinctive vibrational bands corresponds to the octahedral and tetrahedral sites respectively, confirming the establishment of spinel structure using FTIR spectroscopy. The dielectric value of the sample decreases with Ce3+ ion doping till MZCE5 further increase shows increase in dielectric value. The presence of spherical grains, which agglomerate and have a porous morphology revealed by FE-SEM and TEM micrographs with particle size ranging 10–12 nm. The EPR investigation of doping reveals an increase in the g-value. The spin concentration increases from 0.88 × 1023 to 1.023 × 1021 spins/g with increasing Ce3+ ion doping accompanied with decrease in relaxation time (7.108 × 1021 to 4.556 × 1021 sec−1). The lower coercivity, remanence and squareness value upon VSM investigation at RT reveals the superparamagnetic nature of the synthesized MZFC ferrite samples. The nanoparticle shows the potential application for high frequency devices, targeted drug delivery, hyperthermia treatment and ferrofluid.

Enhanced magnetic properties of Ce17Fe76.5Co1Zr0.5B6 alloys by magnetic field heat treatment

In the present work, Ce17Fe76.5Co1Zr0.5B6 ribbons were prepared by a direct melt spinning method. The effects of chamber pressure and magnetic field annealing temperature on the magnetic properties and microstructures of the alloys were investigated. The grain size and content of Ce2Fe14B phase can be changed by adjusting the chamber pressure, and the optimal magnetic performance is obtained at 0.04 MPa. The magnetic properties can be influenced under magnetic field heat treatment. When the annealing temperature is lower than the Curie temperature, the refinement and a uniform distribution of the grains is obtained. The irreversible magnetic susceptibility curve reveals that magnetic field heat treatment enhances the exchange coupling interaction between grains of the Ce2Fe14B phase. When the magnetic field annealing temperature is 438 K, the alloy displays the optimal magnetic properties. Compared with the as-spun sample, the values of intrinsic coercivity (Hci), remanence (Br) and maximum energy product ((BH)max) increase by 3.4%, 9.8% and 18.7%, respectively. This work provides an effective approach by which to enhance the magnetic properties of Ce–Fe–B alloys.

Tunning of rheological and magnetic properties of Ni doped magnetite based magnetic nanofluid

The effect of nickel doping on the structural and magneto-rheological properties of Fe3O4 based nanomagnetic fluids (NMFs) having the composition NixFe3-xO4 (0 ≤ x ≤ 0.8) has been studied. The structural and compositional analysis confirmed the nanoscale regime (∼10 nm) of samples prepared by chemical co-precipitation method and structural analysis was performed by XRD pattern to ascertain the effect of Ni doping. From the UV–Visible spectroscopy studies, the energy band gap was found to be in the range 2.2–3.0 eV with increase in Ni concentration. The magnetic measurements reveal the lower values of coercivity and remanence. The magneto-rheological measurements confirm that in all samples shows a non-Newtonian shear thinning behavior and the increase of viscosity and dipolar interactions while increasing the magnetic field. Whereas in absence of field, higher grain boundaries enhance the interlayer friction and higher viscosity with Ni doping.

Soft solution growth of magnetite-maghemite nanocrystals in crosslinked chitosan templates and their superparamagnetic properties

Crosslinked chitosan/iron oxide nanocomposites (CC/IO) were synthesized at low temperatures using aqueous systems, i.e. hydrothermal and refluxing methods. The CC templates derived from various concentrations of tripolyphosphate crosslinker were used as host materials. The Fe2+ and Fe3+ ions with 1:2 molar ratio were adsorbed into the CC templates by the swelling, allowing to form CC/Fe2+Fe3+ precursors. The CC/IO nanocomposites were created by treating the precursors in NaOH solution using hydrothermal and refluxing methods. The CC/IO nanocomposites contained magnetite-maghemite nanocrystals with quadrilateral shape of 10 − 14 nm embedded in the CC templates. Superparamagnetism was obtained in the CC/IO nanocomposites, which had maximum magnetization (Mmax) values ranging from 8.6 to 15.2 emu/g and coercivity and magnetic remanence values close to zero. The cell viability of CC/IO nanocomposites ranged from 80 to 89%, demonstrating high safety for mammal. The CC/IO nanocomposites were considered to be potential superparamagenetic candidates for alternative medical applications.

Preparation and Characterisation of Composite Magnetite Fe3O4-Activated Carbon as Adsorben of Phenol

Preparation and characterization of magnetite Fe3O4-palm shell activated carbon composite has been carried out as an adsorbent of phenol compounds. Composites were preparation using the co-precipitation method by mixing Fe3O4 magnetite and suspension of activated carbon in water at 2:1 ratio by co-precipitation method. The functional groups, morphology and magnetization of the composites were characterized by FTIR, XRD, SEM-EDX and VSM. The XRD characterization result showed that the irregular activated carbon diffraction pattern on the composite showed that the carbon structure was amorphous and the peak was typical of Fe3O4 at an angle of 2θ 35.3961˚ with the distance of the diffraction plane or d = 2.53387Ǻ. VSM characterization shows the magnetic properties of magnetite are super paramagnetic with the resulting magnetization value of 15.93 emu/g, the remanence value (Mr) is 1.79 emu/g and the coercivity value (Hc) is 131.64 Oe. Adsorbent used for phenol adsorption with optimum at pH 6 with adsorption capacity was      6.71 mg/g, 120 minute contact time with adsorption capacity was 9.63 mg/g and the amount of phenol absorbed reached equilibrium a concentration of 300 mg/L of phenol with an adsorption capacity is 58.6 mg/g. The kinetics parameter showed that the adsorption followed pseudo second-order model.

Magnetic Properties of Ancient Sediments Bengawan Solo, Central Java-East Java, Indonesia

Information about the eruption of Mount Lawu in Central Java Province in 1885 and Mount Merapi in D.I. Yogyakarta in 2010 became a source for estimating the presence of magnetic minerals which underwent a sedimentation process in the Bengawan Solo River from upstream (Wonogiri) - downstream (Bojonegoro). The results we get of the magnetic susceptibility distribution of the Bengawan Solo sediments reveal that the sediment from the upper reaches of the Bengawan Solo River has a low frequency magnetic susceptibility value in upstream of around 1,080.23×10−8 m3/Kg - 2,780.77×10−8 m3/Kg, the middle part is 74.40×10−8 m3/Kg - 1,735.90×10−8 m3/Kg, and downstream 17.57×10−8 m3/Kg - 1,620.53×10−8 m3/Kg. The value of magnetic susceptibility decreased significantly from upstream to downstream. High susceptibility indicates the sample contains metal elements. In determining iron oxide, we use X-Ray Fluorescence assisted by X-Ray Diffractometer testing to determine magnetic minerals. X-Ray Fluorescence confirm metal oxide in the sample. There are Al and Fe confirm the presence of magnetic properties in sedimentation. The Vibrating Sample Magnetometer confirmed that the Bengawan Solo sediment has a magnetic saturation about 0.06 - 9.50 (emu/g), a magnetic remanent around 0.001 - 0.575 (emu/g) and coercivity field of around 10 - 60.15 (Oe). X-Ray Diffractometer pattern confirm the mineral structures, namely Coesite, Magnetite, Cristobalite, Portlandite, Quartz, Anatase, Goethite, Tridymite, Gibsyte, Stishovite, Grasullaria, Labradorite and Wuestite. These results indicate the novelty of sediments from Bengawan Solo, Central Java to East Java. HIGHLIGHTS We found several important points in this research: The Bengawan Solo River is formed from several formations and lifting from faults The Bengawan Solo River is rich in minerals formed from metal oxides The magnetic value decreases with the distance from Mount Lawu The Bengawan Solo River has confirmed ferromagnetic properties from the S-type hysterisis curve With low magnetic remanent values, low saturation magnetism and high magnetic corrosivity GRAPHICAL ABSTRACT

Magnetic Properties and Biocompatibility of Different Thickness (Pd/Fe)n Coatings Deposited on Pure Ti Surface via Multi Arc Ion Plating.

The different thickness (Fe/Pd)n coatings were prepared by vacuum ion plating technology on a pure Ti substrate. The (Fe/Pd)n coatings were magnetized using an MC-4000 high-pressure magnetizing machine. Then, the effect of the (Fe/Pd)n coating thickness on the magnetic properties was studied. The surface and section morphology, composition, phase structure, magnetic properties, and biocompatibility of the (Fe/Pd)n coatings were studied by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and CCTC-1 digital flux field measurement. The results showed that the (Fe/Pd)n coatings were granular, smooth, and compact, without cracks. In addition the (Fe/Pd)n coatings formed an L10 phase with a magnetic face-centered tetragonal-ordered structure after heat treatment. With the increase in the thickness of (FePd)n coatings, the content of L10 FePd phase increased and the remanence increased. The remanence values of the Fe/Pd, (Fe/Pd)5, (Fe/Pd)10, and (Fe/Pd)15 magnetic coatings were 0.83 Gs, 5.52 Gs, 7.14 Gs, and 7.94 Gs, respectively. Additionally, the (Fe/Pd)n magnetic coatings showed good blood compatibility and histocompatibility.

A new insight on evolution of texture and cellular structure of P/M processed Sm2Co17 permanent magnets and their effect on magnetic properties

Sm2Co17 type permanent magnets were prepared by a novel processing technique involving pulsed magnetization followed by cold isostatic pressing (CIP). The magnetic properties and microstructure of the CIPed magnetswere compared with those of the magnets processed through conventional uniaxial compaction in a transverse field press (TP)and heat treated under identical conditions. Enhanced values of remanence (Br ~ 10.7 kG) and energy product [(BH)max ~ 29 MGOe] were obtained in the CIPed magnetsas compared to those of the TP magnets[Br ~ 10 kG and (BH)max ~ 25 MGOe]. However, the values of intrinsic coercivity (iHc) and knee field (Hk) of CIPed magnet were found to be lower than those of the TP magnet.The results were explained on the basis of the difference in texture, microtexture and microstructure obtained in these magnets due to different processing methods adopted.

Magnetization dynamics of iron oxide super paramagnetic nanoparticles above blocking temperature

Magnetic characterizations of synthesized superparamagnetic Iron-Oxide nanoparticles have been carried out at various constant temperatures. As magnetization versus magnetic field (M−H) curve verifies the superparamagnetic nature of nanoparticles, M−H curve has been analysed to verify the superparamagnetic behavior of synthesized nanoparticles. Structure and morphology has been characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM).The XRD confirms the cubic spinel structure of prepared nanoparticles. Cubical shaped morphology is observed from the TEM image. The reaction temperature is observed to critically affect the particle size and modification of magnetic properties. Further, the M−H curve has been analysed to fit the Langevin function and size distribution of nanoparticles has also been studied. The experimentally measured magnetization curve found to fit the theoretically calculated Langevin function satisfactorily. The typical intrinsic magnetization of prepared nanoparticles show superparamagnetism and observed to follow the sigmoid function with negligible remanence and coercivity value. The particles are found to be agglomerated with a size distribution of 10 - 30 nm.

Combined experimental and DFT studies of Co82Zr12V6-xBx melt-spun ribbons to investigate structure and magnetic properties

For the development of rare-earth free permanent magnets with better performance to cost ratio, V and B dopings were employed to enhance the hard magnetic properties of Zr-Co-V-B alloys. The effect of V and B microalloying additions on the magnetic properties, phase stability and microstructure of the metastable Co5Zr phase have been investigated with experimental measurements together with first principles based on the DFT (Density Functional Theory) calculations. This study also investigates the effects of annealing at different temperatures on the intrinsic and extrinsic magnetic properties of Co82Zr12V6-xBx melt-spun ribbons. Rapidly solidified Co82Zr12V6-xBx (x = 1, 2, 3) alloy ribbons were produced by melt-spinning. For as-spun Co82Zr12V6-xBx (x = 1, 2, 3) ribbons, the coercivityHcdecreases from 2.34 kOe to 0.008 kOe with an increasing × value from 1 to 3.The amorphous alloy ribbons were annealed in a vacuum furnace at a series of temperatures of 600 °C, 650 °C, 700 °C and 750 °C each for 30 min. The XRD analysis showed the presence of two soft magnetic phases (fcc-Co and Co23Zr6), accompanied with a hard phase Co5Zr in ribbons thus leading to the desired hard/soft structure and the amount of both (hard and soft) phases increased with the annealing temperature. Coercivity was found to increase upon annealing treatment. The phase stabilities of the Co82Zr12V6-xBx ribbons were calculated from the total energy by the DFT calculations in this work. The calculated magnetic anisotropy energies have been compared to that of experimental coercivity values. Annealed sample Co82Zr12V5B1 showed the maximum coercivity value of 3.58 kOe due to the formation of a high volume fraction of hard magnetic phase (Co5Zr) and evenly distributed finer grains throughout the matrix. However, annealing under the same conditions resulted in lower coercivity of about 0.088 kOe and 1.61 kOe for Co82Zr12V3B3 and Co82Zr12V4B2 samples, respectively. Although sample Co82Zr12V4B2 exhibited higher remanence (42.80 emu/g) and maximum magnetization value with the applied field of 17 kOe (i.e. M17 = 77.70 emu/g) compared to Co82Zr12V3B3 sample.

Coating of aluminum substrates with nanostructured Pd–Ni alloys by electrodeposition

Pd–Ni alloys are electrodeposited onto low-purity aluminum substrates varying both the composition of the feeding solution and the applied electrodeposition potential. It is found that the initial nucleation-and-growth mechanism in every case is well described by a 3D-type nucleation process. The resulting deposits consist of Pd–Ni alloys of different compositions, all electrocrystallized in a disordered fcc phase; depending on the electrodeposition parameters, different morphologies and compositions are obtained. It is found that when the electrodeposition potential is high and the Pd content in the feeding solution is low, the substrate coating is more efficient and the deposit morphology tends to refine into dendritic-like structures, making this kind of deposit quite interesting for using as electrodes in electrochemical devices. Room temperature magnetic measurements indicate that the samples are soft ferromagnetic with negligible demagnetizing effects. Dendritic and spheroidal-like Pd-rich deposits exhibit larger remanence values and are more coercive than those with higher Ni content due to the dependence of the anisotropy constant on the alloy composition.

Preparation of Mn–Zn ferrite ceramic using stereolithography 3D printing technology

In this work, tailored Mn–Zn ferrite ceramics are prepared by stereolithography (SLA) 3D printing technology, and its performances are measured utilizing the printing accuracy, magnetic properties, density, and microstructures. The major obstacle forming difficultly by single curing of self-made ferrite pastes with increasing solid content in the printing process is removed by using six scanning numbers. In addition, the prediction formulas of the linewidth and curing depth are established. The printing process parameters, namely scanning space, scanning speed, and laser power, are optimized at 2 μm, 2500 mm/s, and 240 mW, respectively. The size of convex platform bigger than 1 mm × 1.2 mm possessing circular and square holes with a diameter and a side length of 0.2 mm can be printed using the printing process parameters above. Specifically, the sintering temperature and holding time below 1200 °C and 90 min, respectively, are optimized conducive limits. The sintered parts show a density of 4.04 g/cm3 and a saturation magnetization of 58.6 emu/g, along with a small value of coercivity and remanence. The SLA-3D printing, debinding, and sintering technologies can print the complex shapes Mn–Zn ferrite ceramics using the proposed process.

The Magnetic Properties of Fe/Cu Multilayered Nanowires: The Role of the Number of Fe Layers and Their Thickness.

Multi-segmented bilayered Fe/Cu nanowires have been fabricated through the electrodeposition in porous anodic alumina membranes. We have assessed, with the support of micromagnetic simulations, the dependence of fabricated nanostructures’ magnetic properties either on the number of Fe/Cu bilayers or on the length of the magnetic layers, by fixing both the nonmagnetic segment length and the wire diameter. The magnetic reversal, in the segmented Fe nanowires (NWs) with a 300 nm length, occurs through the nucleation and propagation of a vortex domain wall (V-DW) from the extremities of each segment. By increasing the number of bilayers, the coercive field progressively increases due to the small magnetostatic coupling between Fe segments, but the coercivity found in an Fe continuous nanowire is not reached, since the interactions between layers is limited by the Cu separation. On the other hand, Fe segments 30 nm in length have exhibited a vortex configuration, with around 60% of the magnetization pointing parallel to the wires’ long axis, which is equivalent to an isolated Fe nanodisc. By increasing the Fe segment length, a magnetic reversal occurred through the nucleation and propagation of a V-DW from the extremities of each segment, similar to what happens in a long cylindrical Fe nanowire. The particular case of the Fe/Cu bilayered nanowires with Fe segments 20 nm in length revealed a magnetization oriented in opposite directions, forming a synthetic antiferromagnetic system with coercivity and remanence values close to zero.

Investigation of Ferrimagnetic Sr-hexaferrite Nanocrystals for Clinical Hyperthermia

Sr-hexaferrite samples were produced via the conventional ceramic method. X-ray diffractometry (XRD) patterns confirmed the single nanocrystal phase as Sr-hexaferrite where any pattern peaks of unreacted Fe2O3 phase were not detected. The mean crystallite size values were determined to be 44.12±3.4nm and 41.2±3.2nm for SHF-O1 and SHF-O2, respectively. The chemical bonding peaks of our sample indicated that the structure of Sr-hexaferrite formation was confirmed by FTIR spectra result. Scanning electron microscopy (SEM) images indicated clearly observed porosity regions with relative densities as high as 94% and 87% for SHF-O1 and SHF-O2 samples.The vibrating sample magnetometry (VSM) of each sample at 2K and under a magnetic field of 10 kOe yielded saturation magnetizations, Ms of 93.5 and 94.1 emu/g; remanence values, Mr of 76.4 and 67.8 emu/g for SHF-O1 and SHF-O2, respectively. The magnetization loops of both samples indicated a soft ferrimagnetic behaviour in which the saturation magnetizations were higher than those measured at room temperature in the previous studies. The coercivities, Hc were measured to be 150Oe for both samples. The squareness values, SQR (Mr/Ms) were measured to be high, approximately 0.82 and 0.72 for SHF-O1 and SHF-O2, respectively. Depending on the adequate values of magnetization and coercivity along with small mean crystallite size and low porosity values of the obtained Sr-hexaferrite samples, we estimate that these samples are likely to be evaluated further for the potential use as thermoseeds in the field of clinical hyperthermia.

Relaxation mechanism in Ni0.5Zn0.5Fe2O4 nanocrystalline ferrite at a lower temperature

In this paper, the relaxation mechanism at a lower temperature in the Ni0.5Zn0.5Fe2O4 sample has been discussed in detail. The sol gel method has been used to prepare the Ni0.5Zn0.5Fe2O4 sample. The Rietveld refinement of XRD gives the cubic crystal structure (a = 8.39 Å) and average crystallite size ∼ 40 nm. The EDAX technique confirms the elemental composition in the sample. The M−H loop shows the remanence and coercivity value at 5 K temperature which indicates that the magnetic domains are exist. The saturation magnetization at 5 T field is also decreasing with increasing temperature which supports that the thermal energy destroys the domain size. The ZFC & FC curves show the relaxation mechanism of at lower temperature. The 2Hm value is decreasing with increasing temperature which suggests that the magnetic domain is decreasing with increasing temperature which support the relaxation at lower temperature.