Remanence Ratio Research Articles

Structural and magnetic properties of BaFe9.95Al2Mg0.05O19 tuned through sintering temperature

The sintering temperature is a key way to tune the structural and magnetic properties of M-type hexaferrites. Here the effect of BaFe9.95Al2Mg0.05O19 M-type hexagonal Ba-hexaferrites, was studied. X-ray diffraction analysis revealed the presence of Fe2O3 impurity phases in all samples. The results showed that as the sintering temperature increased, the saturation magnetization (Ms) and remanence ratio (Mr/Ms) initially increased, then decreased at higher temperatures. On the other hand, the coercivity (Hc) and magnetocrystalline anisotropy field (Ha) decreased first, then increased. The average grain size (D) consistently grew between 800–2800 nm with increase in pre-sintering temperature. The optimal magnetic properties of BaFe9.95Al2Mg0.05O19 were achieved at a pre-sintering temperature of 1280 °C, with Ms = 49.94 emu g−1, Hc = 4.99 kOe, Ha = 1.5 kOe, and mB = 9.4097 μB. The findings suggest that magnetic properties of M-type hexagonal strontium ferrite can be significantly enhanced by optimizing the pre-sintering temperature, which has implications for the development of high-performance self-biased circulators, Magnetic filters and other magnetic applications.

Structure and Performance Optimization of Co Magnetic Thin Films Deposited by Vacuum Evaporation Coating.

Co magnetic films are widely used in high-frequency magnetic recording and vertical magnetic recording due to their high saturation magnetization and magnetocrystalline anisotropy. In this work, ferromagnetic Co magnetic films were prepared on copper substrate by vacuum evaporation combined with heat treatment (H2 atmosphere), to investigate the impact of film thickness and annealing temperature on microstructure and magnetic properties. The results show that with the increase in annealing temperature, the Co thin film physical phase does not change significantly, the crystallinity increases, and the grain size increases, which is consistent with the results obtained from the SEM morphology map of the sample surface, leading to an increase in coercivity. By annealing experiments (atmospheric atmosphere) on Co magnetic films with and without an Al protective layer, as shown by scanning electron microscopy microscopic characterization results, it was verified that the Al layer can protect the inner Co layer from oxidation. As the film thickness increases from 10 to 300 nm, the magnetic properties of Co films change significantly. The saturation magnetization gradually increases from 0.89 to 5.21 emu/g, and the coercivity increases from 124.3 to 363.8 Oe. The remanence ratio of the 10 nm magnetic film is 0.82, which is much higher than the film remanence ratio of 0.46 at 50 nm. This is because when the thickness of the film is between 10 and 50 nm, the magnetic moments partially deviate from the in-plane direction, and the out-of-plane component reduces the film remanence ratio. This study shows that optimizing annealing temperature and film thickness can effectively control the structure and magnetic properties of Co magnetic films, which is of great significance for the development of the magnetic recording field.

Magnetic, optoelectronic, and rietveld refined structural properties of Al3+ substituted nanocrystalline Ni-Cu spinel ferrites: An experimental and DFT based study

The nanocrystalline Ni0.7Cu0.3AlxFe2-xO4 (x = 0.00: 0.02: 0.10) are prepared through the sol–gel auto combustion route. The structural, surface morphology, magnetic and optoelectronic properties of Al3+ substituted Ni-Cu spinel ferrites have been reported. The crystallinity, phase structure, and structural parameters of the synthesized nanoparticles (NPs) have been determined through X-ray diffraction (XRD) and further refined by maneuvering the Rietveld refinement approach. Both XRD and Rietveld confirm the single phase cubic spinel structure of the investigated materials. Microstructural surface morphology study also confirms the formation of NPs in the highly crystalline state with a narrow size distribution. The Rietveld-refined average crystallite size of the Al3+ doped Ni-Cu ferrite nanoparticles falls in the range (61–71 nm), and the average grain size is found to vary from 59 to 65 nm. All other structural parameters refined by the Rietveld refinement analysis are corroborated to single-phase cubic spinel formation of the NPs. Leveraging a vibrating sample magnetometer (VSM), the consequence of Al3+ substitution on the magnetic parameters is studied. The saturation magnetization (MS) and Bohr magneton are found to decrease with Al3+ substitution. The Remanence ratio and coercivity (HC) are observed to be very low, suggesting the materials are soft ferromagnetic. First-principle calculations were carried out using the density functional theory (DFT) to demonstrate the optoelectronic behavior of the materials. The electronic bandgap is found low as Eg = 2.99 eV for the explored materials with observing defect states at 0.62 eV. The optoelectronic properties of Al3+ substituted Ni-Cu ferrite NPs have been characterized through the DFT simulation for the first time, demonstrating their potentiality for optoelectronic device applications. The materials' optical anisotropy is observed along the x-axis, which manifests their tunability through light-matter interaction.

Magnetic Properties of Australasian Tektites From South China

AbstractSouth China, the northern part of the Australasian strewn field (AASF) of tektites and microtektites is located at the uprange of the hypothesized source crater that is still unconfirmed. Magnetic properties of impact glasses are an important indicator of their source materials and thermal history. Extensive magnetic investigations have been performed on various AASF tektites sampled from both the Indochina Peninsula and further south, but such information remains sparse for those sampled from South China. Here, we present a detailed rock magnetism study for both Muong Nong‐type and splash‐form AASF tektites from South China, showing that all the tektites have rather weak remanent magnetization, but ferromagnetic information can be extracted from their dominating paramagnetic signal. Signals caused by superparamagnetic particles are elusive, but those of single domain magnetite are detected in the splash‐form tektites, and signals of pseudo‐single domain magnetite are discovered in the Muong Nong‐type tektites. Each morphological type of tektites from a same geographic area exhibits large dispersions in their magnetic properties. Across the entire AASF, the Muong Nong‐type tektites from South China exhibit the lowest average magnetic susceptibility, and the splash‐form tektites exhibit the smallest average natural remanent magnetization and ratio of equivalent magnetization. The observed heterogeneous magnetic properties are mainly caused by the different contents and sizes of magnetic particles, which can be explained by the different shock level and/or cooling history of the tektite melts. Micro‐sized immiscible Fe‐S spherules in the Muong Nong‐type tektites from South China were likely originated from the pre‐impact target.

Study of the anisotropic Sm2Fe17N3 powders with high performance

The strip casting technique was first used in this work to prepare the Sm2Fe17 parent alloys. Next, the Sm2Fe17N3 powders were synthesized using a gas–solid reaction of Sm2Fe17 powders with N2. Then, the anisotropic Sm2Fe17N3 powders with high performance were prepared by a surfactant-assisted grinding method in gasoline solvent. It was found that the coercivity (iHc) of ground powders increases with decreasing the average particle size (Dm), while the saturation magnetization (Ms) decreases. The maximum value of iHc of 17.5 kOe was obtained at the Dm = 1.3 µm. The ground powders with Dm of 3.1 µm show a remanence ratio (Mr/Ms) over 95% and a maximum energy product [(BH)max] of 35 MGOe. The Sm2Fe17N3 powder exhibited a very high iHc of 36.1 kOe at 10 K. Above 300 K, Sm2Fe17N3 powders mixed with epoxy resin showed a low remanence temperature coefficient of α(RT-100°C) = −0.077% °C−1.

Magnetic Response of Nano/Microparticles into Elastomeric Electrospun Fibers

Combining magnetic nanoparticles (MNPs) with high-voltage processes to produce ultra-thin magnetic nanofibers (MNFs) fosters the development of next-generation technologies. In this study, polycarbonate urethane nanofibers incorporating magnetic particles were produced via the electrospinning technique. Two distinct types of magnetic payload were used: (a) iron oxide nanoparticles (IONPs) with an average size and polydispersity index of 7.2 nm and 3.3%, respectively; (b) nickel particles (NiPs) exhibiting a bimodal size distribution with average sizes of 129 nanometers and 600 nanometers, respectively, and corresponding polydispersity indexes of 27.8% and 3.9%. Due to varying particle sizes, significant differences were observed in their aggregation and distribution within the nanofibers. Further, the magnetic response of the IONP and/or NiP-loaded fiber mats was consistent with their morphology and polydispersity index. In the case of IONPs, the remanence ratio (Mr/Ms) and the coercive field (Hc) were found to be zero, which agrees with their superparamagnetic behavior when the average size is smaller than 20-30 nm. However, the NiPs show Mr/Ms = 22% with a coercive field of 0.2kOe as expected for particles in a single or pseudo-single domain state interacting with each other via dipolar interaction. We conclude that magnetic properties can be modulated by controlling the average size and polydispersity index of the magnetic particles embedded in fiber mats to design magneto-active systems suitable for different applications (i.e., wound healing and drug delivery).

Enhanced magnetic properties of Sr0.7Ce0.3Fe11.7Zn0.3O19 by tuning pre-sintering temperature

In this work, pre-sintering temperature was tuned to investigate its effect on the structural and magnetic properties of oriented M-type hexagonal strontium ferrite Sr0.7Ce0.3Fe11.7Zn0.3O19. X-ray diffraction pattern shows that Fe2O3 and CeO2 impurity phases exist in all samples. As pre-sintering temperature increased, both saturation magnetization (Ms) and remanence ratio (Mr/Ms) first increased and then decreased. In contrast, coercivity (Hc) and magnetocrystalline anisotropy field (Ha) first decreased and then increased as pre-sintering temperature went up. The average grain size (D) increases monotonously with pre-sintering temperature. At pre-sintering temperature of 1200 ℃, Sr0.7Ce0.3Fe11.7Zn0.3O19 achieved optimal magnetic properties of Ms = 58.24 emu/g, Mr/Ms = 0.95, Hc= 1816 Oe, Ha= 10433 Oe and K1 = 1.51 × 105 J/m3. This work shows that the magnetic properties of M-type hexagonal strontium ferrite could be significantly improved by optimizing the pre-sintering temperature, which helps the design of high-performance and self-biased circulator.

High remanence ratio of aluminum substituted hexagonal barium ferrite films for self-biased microwave devices

A high remanence ratio of hexagonal barium ferrite film is urgently needed for self-biased microwave devices. In this work, the aluminum-substituted hexagonal barium ferrite films (BaFe(12−x)AlxO19) with different substituting concentrations (x = 0, 1.5, 2, 2.5, 3) were deposited on the Al2O3 substrate by pulsed laser deposition method using self-sintered BaFe(12−x)AlxO19 target. Firstly, the targets with different Al concentrations were sintered by the solid phase method and exhibited high dense, uniform microstructure, and high purity. Then, the influence of the Al ions concentration on the crystal structure, morphology, and magnetic and microwave properties of BaFe(12−x)AlxO19 films was studied in detail. Structural characterizations confirm that the Al prefers to substitute for 2a, 4f2 and 2b sites and promotes the grain (formed as single-domain) orientation growth, which results in a decrease in the saturation magnetization, an increase of remanence ratio and anisotropy field. Consequently, a high remanence ratio of 95 % was obtained for BaFe(12−x)AlxO19 film at x = 3, and also displays a high anisotropy field (27.7 kOe), a low saturation magnetization (1758 G) and an appropriate ferromagnetic resonance linewidth (～436 Oe), which can be applied in self-biased devices.

Microstructure and Magnetic Properties Dependence on the Sputtering Power and Deposition Time of TbDyFe Thin Films Integrated on Single-Crystal Diamond Substrate

As giant magnetostrictive material, TbDyFe is regarded as a promising choice for magnetic sensing due to its excellent sensitivity to changes in magnetic fields. To satisfy the requirements of high sensitivity and the stability of magnetic sensors, TbDyFe thin films were successfully deposited on single-crystal diamond (SCD) substrate with a Young’s modulus over 1000 GPa and an ultra-stable performance by radio-frequency magnetron sputtering at room temperature. The sputtering power and deposition time effects of TbDyFe thin films on phase composition, microstructure, and magnetic properties were investigated. Amorphous TbDyFe thin films were achieved under various conditions of sputtering power and deposition time. TbDyFe films appeared as an obvious boundary to SCD substrate as sputtering power exceeded 100 W and deposition time exceeded 2 h, and the thickness of the films was basically linear with the sputtering power and deposition time based on a scanning electron microscope (SEM). The film roughness ranged from 0.15 nm to 0.35 nm, which was measured by an atomic force microscope (AFM). The TbDyFe film prepared under a sputtering power of 100 W and a deposition time of 3 h possessed the coercivity of 48 Oe and a remanence ratio of 0.53, with a giant magnetostriction and Young’s modulus effect, suggesting attractive magnetic sensitivity. The realization of TbDyFe/SCD magnetic material demonstrates a foreseeable potential in the application of high-performance sensors.

Suppression Effect on the Domain Wall Tilting in Synthetic Antiferromagnetic Racetrack Driven by the Spin–Orbit Torque

The perpendicularly magnetized synthetic antiferromagnet is an ideal candidate for racetrack memory due to the low stray field, allowing the closely packed domain wall (DW) and high recording density. Herein, the dynamics of DW motion driven by the magnetic field and current are investigated in the synthetic antiferromagnetic (SAF) Ta/Pt/Co/Pt/Ru/Pt/Co/Ta structures with different thicknesses of the top magnetic (TM) Co layers. The results illustrate that the direction of the DW motion will be reversed when the field pulse is below a critical field for the sample with a negligible remanence ratio. As for the current‐driven DW motion case, a significant enhancement of the DW velocity, as well as a strong suppression effect on the tilting of DW's plane due to the strong interlayer exchange coupling for the SAF structure, is found. The fast DW velocity and small tilting angle in SAF are valuable for spintronic racetrack memories.

Size-dependent magnetic and magnetoresistance properties of Co2 FeGa nanowires

Co2FeGa Heusler alloy nanowires with diameters of about 30, 60 and 110 nm were prepared using a template-assisted electrochemical deposition method. We observe the different angular dependences of coercivity and remanence ratio for these samples. Magneto-transport measurements show that the 30 nm diameter Co2FeGa nanowires has a large magnetoresistance up to −56%, which is much higher than 60 and 110 nm diameter Co2FeGa nanowires. This is the first time that the magnetoresistance properties of Co2FeGa nanowires were presented.

Hardening of Cobalt Ferrite Nanoparticles by Local Crystal Strain Release: Implications for Rare Earth Free Magnets.

In this work, we demonstrate that the reduction of the local internal stress by a low-temperature solvent-mediated thermal treatment is an effective post-treatment tool for magnetic hardening of chemically synthesized nanoparticles. As a case study, we used nonstoichiometric cobalt ferrite particles of an average size of 32(8) nm synthesized by thermal decomposition, which were further subjected to solvent-mediated annealing at variable temperatures between 150 and 320 °C in an inert atmosphere. The postsynthesis treatment produces a 50% increase of the coercive field, without affecting neither the remanence ratio nor the spontaneous magnetization. As a consequence, the energy product and the magnetic energy storage capability, key features for applications as permanent magnets and magnetic hyperthermia, can be increased by ca. 70%. A deep structural, morphological, chemical, and magnetic characterization reveals that the mechanism governing the coercive field improvement is the reduction of the concomitant internal stresses induced by the low-temperature annealing postsynthesis treatment. Furthermore, we show that the medium where the mild annealing process occurs is essential to control the final properties of the nanoparticles because the classical annealing procedure (T > 350 °C) performed on a dried powder does not allow the release of the lattice stress, leading to the reduction of the initial coercive field. The strategy here proposed, therefore, constitutes a method to improve the magnetic properties of nanoparticles, which can be particularly appealing for those materials, as is the case of cobalt ferrite, currently investigated as building blocks for the development of rare-earth free permanent magnets.

Highly c-axis oriented W-type hexaferrites SrNi2ScxFe16-xO27 (x = 0.70, 0.75, 0.80 and 0.85) for the design of self-biased circulator at Ku band

Highly oriented W-type hexaferrites SrNi2ScxFe16-xO27 (SrW, x = 0.70, 0.75, 0.80 and 0.85) are fabricated via ceramic process and magnetic orientation to meet design requirements of self-biased circulators. The orientation degree reaches 0.81 when Sc3+ substitution content x is 0.75. The XRD refinement results in consideration of orientation illustrate the strong c-axis anisotropy texture of SrW. SEM images show significant uniformity in grain growth with c-axis stays vertical to sample plane. Consequently, the corresponding remanence ratio Mr/Ms reaches as high as 0.92, which is indispensable to reduce low field loss (LFL) as much as possible in the design of self-biased circulators. According to simulation results, the self-biased microstrip circulator based on this SrW material (x = 0.75) realizes ideal functions in circular transmission operating at Ku band.

Magnetic Properties Regulation of FeGa and FeGaNi Films with Oblique Magnetron Sputtering

Magnetic FeGa and FeGaNi films with an in-plane anisotropy were deposited by employing oblique magnetron sputtering. With the increase in oblique angle, the crystallite size of FeGa decreases, which indicates that oblique sputtering can refine the crystallite size. The remanence ratio of FeGa films increases from 0.5 to 0.92 for an easy axis, and the coercivity increases with the decrease in the crystallite size. The calculated static anisotropic field shows that the in-plane magnetic anisotropy can be induced by oblique sputtering and the strength increases with the oblique sputtering angle. After doping Ni by co-sputtering, FeGaNi films exhibit a stable remanence ratio at 0.8, low coercivity and good anisotropy. With the low sputtering power of the Ni target, there is a competitive relationship between the effect of crystallite size and Ni doping which causes the coercivity of FeGaNi films to first increase and then decrease with the increase in the oblique angle. The FeGaNi film also shows high anisotropy in a small oblique angle. The variation of coercivity and anisotropy of FeGaNi films can be explained by the crystalline size effect and increase in Ni content. For the increasing intensity of collisions between FeGa and Ni atoms in the co-sputtering, the in-plane magnetic anisotropy increases first and then decreases. As a result, the magnetic properties of FeGa films were examined to tailor their magnetic softness and magnetic anisotropy by controlling the oblique sputtering angle and Ni doping.

Barium hexaferrites with narrow ferrimagnetic resonance linewidth tailored by site‐controlled Cu doping

AbstractBarium hexagonal ferrites exhibiting unique self‐biasing characteristics have great potential for application in planar microwave devices, such as self‐biased circulators. Cu doping is an effective method to tailor their anisotropy field and ferrimagnetic resonance (FMR) linewidth to meet the requirements for low‐frequency low‐loss microwave devices. However, the regulation mechanism of Cu doping is still obscure, and its regulation effect is not optimized. Here, the magnetic and microwave properties of two groups of barium hexaferrites with site‐controlled Cu doping are reported. The diffusion dynamics of Cu2+ ions are comprehensively investigated, revealing significant differences in the concentration distribution and polycrystalline morphology, when comparing CuO as a reactant and sintering additive. The accumulation of Cu2+ ions at grain boundaries contributes to the increase in coercivity, whereas the dispersion of Cu2+ ions in crystallites leads to the decrease in the anisotropy field. Moreover, by introducing Cu2+ ions into the interstitial positions of the lattice, barium hexaferrites with a narrow FMR linewidth of 303 Oe and a high remanence ratio of 0.82 are achieved. These results represent the lowest FMR linewidth reported in polycrystalline hexagonal ferrites and prove the great technological value and commercial potential of Cu‐doped barium hexaferrites for next‐generation planar microwave devices.

Greigite (Fe3S4) Formation in Artificial Sediments via Solid‐State Transformation of Lepidocrocite

AbstractGreigite (Fe3S4) is a ferrimagnetic iron‐sulfide mineral that forms in sediments during diagenesis. Greigite growth can occur diachronously within a stratigraphic profile, complicating or overprinting environmental and paleomagnetic records. An important objective for paleo‐ and rock‐magnetic studies is to identify the presence of greigite and to discern its formation conditions. Greigite detection remains, however, challenging and its magnetic properties obscure due to the lack of pure, stable material of well‐defined grain size. To overcome these limitations, we report a new method to selectively transform lepidocrocite to greigite via the intermediate phase mackinawite (FeS). In‐situ magnetic characterization was performed on discrete samples with different sediment substrates. Susceptibility and chemical remanent magnetization increased proportionally over time, defining two distinct greigite growth regimes. Temperature dependent and constant initial growth rates indicate a solid‐state FeS to greigite transformation with an activation energy of 78–90 kJ/mol. Low and room temperature magnetic remanence and coercivity ratios match with calculated mixing curves for superparamagnetic (SP) and single domain (SD) greigite and suggest ∼25% and ∼50% SD proportions at 300 and 100 K, respectively. The mixing trend coincides with empirical data reported for natural greigite‐bearing sediments, suggesting a common SP endmember size of 5–10 nm that is likely inherited from mackinawite crystallites. The average particle size of 20–50 nm determined by X‐ray powder diffraction and electron microscopy accords with theoretical predictions of the SP/SD threshold size in greigite. The method constitutes a novel approach to synthesize greigite and to investigate its formation in sediments.

Effect of cobalt substitution in Zn1-xCoxFeCrO4 ferri-chromate: emerging light absorber for degradation of model textile dye

The concentration (x = 0.0 to 1.0) of cobalt doped magnetically separable Zn1-xCoxFeCrO4 ferrite was produced by sol-gel auto combustion utilizing glycine as a fuel. We can deduce that a single-phase cubic spinel system is synthesized based on powder XRD measurements and Rietveld refinement of the Zn1-xCoxFeCrO4 ferrite system. With the increase in cobalt content in the Zn1-xCoxFeCrO4 ferrite system, morphological examination revealed irregularly formed nanostructures ranging in size from 10 nm to 40 nm. When this ferrite system was exposed to TEM examination, similar morphological results were found. The coercivity of the Zn1-xCoxFeCrO4 ferrite system increased as the density and crystallite size were reduced. The remanence ratio rises in proportion to the increase in cobalt content. The visible region's optical characteristics were studied, and a blue shift in the band gap was observed with the increase in concentration of cobalt. The photo catalytic activity of as-synthesized Zn1-xCoxFeCrO4 ferrites on methylene blue (MB) dye degradation was evaluated because the band gap of the catalysts lies in the visible region. Within 85 minutes, the targeted photocatalyst degraded 96.7% of methylene blue, equating to a high degradation reaction rate constant k value up to 0.0089 min−1. As a result, the catalyst has a bright future in terms of environmental remediation. Increased photo catalytic activity is attributed to inhibition of load carrier separation due to crystallinity, proper band energy structure, and morphology of Co2+ doped Zn1-xCoxFeCrO4 ferrite. In addition, our targeted photo catalyst Zn0.25Co0.75FeCrO4 showed good stability and radical scavenger tests suggesting that holes/ hydroxyl radicals were the primary components for increased activity.

Anomalous magnetoresistance and Hall effect in amorphous Pt/TbFeCo thin films

Among the magnetic materials in technological usage, amorphous rare-earth transition metal (RE–TM) alloys are of great interest due to their adjustable magnetic properties and favorable perpendicular magnetic anisotropic (PMA) advantages. In this study, the properties of Tb25Fe61Co14 system with 2, 5, and 10 nm Pt underlayers have been systematically explored by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature and magnetic field dependence of Hall resistivity, magnetoresistivity, and magneto-optic Kerr Effect (MOKE) measurements. According to the results, whole thin films are amorphous in nature and display an out-of-plane magnetic anisotropy without annealing. Increasing the Pt underlayer thickness helps the TbFeCo layer to reach significantly enhanced perpendicular magnetic anisotropic values and visualize the appearance of anomalous magnetoresistance in the Hall effect measurements. The thin films with 5 and 10 nm Pt underlayer has a ratio of remanence magnetization/saturation magnetization (MR/MS) of around 1, which is the out of plane direction of MOKE signal. Besides, the present study also includes some pieces of evidence that might be related to the Berry phase trend.

Annealing enhanced ferromagnetic resonance of thickness-dependent FeGa films

We report the influence of different annealing temperatures on the magnetic property of FeGa thin films. The measurement was done for the film thickness from 42 to 420 nm. Our results show that the annealing temperature affects not only the microstructure but also the ferromagnetic resonance signal of the film. Annealing of a FeGa film improves the in-plane remanence ratio and reduces the in-plane ferromagnetic resonance linewidth by a factor of five. This annealing treatment promotes film texture and releases compressive stresses in the film. Our results demonstrate that the structural control via annealing is viable. The necessary magnetic softness of the FeGa film for microwave applications can be achieved.

Role of surface defects and anisotropy variation on magnetic properties of copper ferrite nanoparticles prepared by co-precipitation method

Nanocrystalline Cu-ferrite samples were synthesized by co-precipitation method at two different pH. The samples were annealed at various temperatures ranging from 400 to 1000 °C in air for 3 h. Tetragonal Cu-ferrite was observed for the sample prepared at pH = 10.9, whereas the sample prepared at pH = 10.3 showed cubic Cu-ferrite, after annealing at 1000 °C. The average grain sizes were found to be 13 and 19 nm for the as prepared samples synthesized at pH = 10.3 and pH = 10.9 respectively, which was increased with the increase in annealing temperature. Spontaneous magnetization values increased with the decrease in surface defects, whereas coercivity and remanence ratio showed peaks with increase in annealing temperature. The highest magnetic moments of 1.6μB and 2.1μB per molecule were observed at 60K for the tetragonal and cubic Cu-ferrite samples respectively. The highest anisotropy constant (K) of 4.98 × 103 and 16.0 × 103 J/m3 was observed at 60K for the sample prepared at pH = 10.3 and pH = 10.9 respectively. The nonsaturation parameter varies similarly with coercivity and anisotropy constant in these nanoparticle samples. The structural transformation, decrease in surface defects, and anisotropy variation with increasing annealing temperature and grain growth explains the observed magnetic properties.