Magnetic Variations Research Articles

Historical evolution of the geomagnetic declination at the Royal Observatory of Madrid

Abstract. The agonic line, which represents geomagnetic declinations of 0°, recently crossed the Royal Observatory of Madrid (ROM) in December 2021, causing a shift in declination values from west to east. This event constitutes a notable milestone for this significant observatory, where the first geomagnetic observation series commenced around 1855 in Spain. In this work, taking advantage of the occurrence of this event, a detailed study has been conducted to investigate the historical evolution of the magnetic declination at the ROM to decipher prior occurrences of the agonic line crossing this place. Despite the ROM having hosted the first series of geomagnetic measurements in Spain, the present lack of geomagnetic measurements in this observatory makes it necessary to extend the declination measurements to other observatories distributed throughout the Iberian Peninsula to better define the passage of the agonic line since 1855 up to the present. For epochs prior to 1855, a bibliographic search for declination measurements conducted in the Iberian Peninsula has been carried out, complemented by historical data from the HISTMAG database. As a result, a time-continuous curve of geomagnetic declination is generated from 1590 to 2022 at the ROM coordinates. The declination curve reveals that the agonic line also crossed the ROM 400 years ago (around 1600), passing from western to eastern declination values.

Structural, electronic, and magnetic properties of binary zigzag antimonene-phosphorene nanoribbons and their mole fractions with different edge passivation: A DFT investigation

The study focuses on binary antimonene-phosphorene, a two-dimensional semiconductor material known for its high carrier mobility, suitable band gap, and strong environmental stability, making it appealing for electronics and spintronics applications. In this study, using density functional theory, we investigated the structural stability and electronic-magnetic properties of zigzag SbP nanoribbons, as well as single Sb and single P nanoribbons. Various edge passivation (H, F, Cl, O, S) are considered, along with different phosphorus mole fractions. The findings show that SbP structures with 25 % phosphorus mole fractions, as well as those passivated with various atoms, demonstrate strong conformational stability. SbP nanoribbons passivated with H, F, and Cl exhibit non-magnetic semiconductor behavior, while those passivated with O and S display magnetic metallic properties. Maximal magnetization is observed in SbP nanoribbons passivated with single S atoms, particularly magnetizing both Sb and P atoms at the edges. Additionally, SbP nanoribbons passivated with dual O atoms show negative differential resistivity and a complete spin filtering effect (100 %). The study also investigates the variation in magnetization across structures with different phosphorus mole fractions. Overall, the study demonstrates that adjusting phosphorus mole fractions and edge passivation can significantly modify the electronic and magnetic properties of SbP nanoribbons, making them suitable for spintronic nanodevices.

Migratory birds can extract positional information from magnetic inclination and magnetic declination alone.

Migratory birds are able to navigate over great distances with remarkable accuracy. The mechanism they use to achieve this feat is thought to involve two distinct steps: locating their position (the 'map') and heading towards the direction determined (the 'compass'). For decades, this map-and-compass concept has shaped our perception of navigation in animals, although the nature of the map remains debated. However, some recent studies suggest the involvement of the Earth's magnetic field in the map step. Here, we tested whether migratory songbirds, Eurasian reed warblers (Acrocephalus scirpaceus), can determine their position based on two magnetic field components that are also associated with direction finding, i.e. magnetic inclination and magnetic declination. During a virtual magnetic displacement experiment, the birds were exposed to altered magnetic inclination and magnetic declination values that would indicate a displacement from their natural migratory corridor, but the total intensity of the field remained unchanged, creating a spatial mismatch between these components. The response was a change in the birds' migratory direction consistent with a compensatory re-orientation. This suggests that birds can extract positional as well as directional information from these cues, even when they are in conflict with another component of the magnetic field. It remains to be seen whether birds use the total intensity of Earth's magnetic field for navigation.

Long-Lived Magnetization in an Atomic Spin Chain Tuned to a Diabolic Point.

Scaling magnets down to where quantum size effects become prominent triggers quantum tunneling of magnetization (QTM), profoundly influencing magnetization dynamics. Measuring magnetization switching in an Fe atomic chain under a carefully tuned transverse magnetic field, we observe a nonmonotonic variation of magnetization lifetimes around a level crossing, known as the diabolic point (DP). Near DPs, local environment effects causing QTM are efficiently suppressed, enhancing lifetimes by three orders of magnitude. Adjusting interatomic interactions further facilitates multiple DPs. Our Letter provides a deeper understanding of quantum dynamics near DPs and enhances our ability to engineer a quantum magnet.

Monitoring of relative magnetic permeability variation during cyclic bending testing of austenitic steel grade 10Kh18n10t samples

Cyclic bending testing of austenitic chromium-nickel steel grade 10Kh18N10T samples was carried out. Evalution of relative magnetic permeability showed its noticeable increase when the samples became fractured. This increase is related to deformation martensite appearance. Additional experiment showed, that deformation martensite formation starts before the actual destruction of the sample.

Assessment of the Weimer Geomagnetic Perturbation Model for High‐Latitude Positioning and Navigation

AbstractThe Geomagnetism Group at the National Centers for Environmental Information (NCEI), in collaboration with the Cooperative Institute for Research in Environmental Sciences (CIRES), along with various government and industry partners, specializes in developing and providing access to Earth's internal magnetic field models. These models are crucial for applications such as compass navigation and wellbore positioning, offering reference values for the geomagnetic field (total field, dip or inclination, and declination) at any location across the Earth. This study assesses the Weimer geomagnetic perturbation model, proposed by Weimer in 2013, which is an empirical model of magnetic field variations at high latitudes driven by solar wind measurements, as a candidate for capturing geomagnetic field variations in high‐latitude areas. We compare the geomagnetic field variations predicted by the Weimer model against data from the INTERMAGNET and SuperMAG observatory networks. Our findings indicate that the Weimer model achieves a reduction in the standard deviations of high‐latitude magnetic field variations by approximately 20%–30% once quiet‐time baselines are removed from the data set. Furthermore, we compare the performance of the Weimer model against the Space Weather Modeling Framework's Geospace model during specific geomagnetic storms in 2017 and 2018, and we find that the Weimer model is more effective in predicting magnetic variations at high latitudes than the Geospace model during these storms. Additionally, comparisons to magnetometer data collected from high‐latitude directional‐drilling operations align with the trends observed in comparisons with INTERMAGNET and SuperMAG observatory data, confirming the Weimer model's reliability and effectiveness for such applications.

Paleomagnetic Secular Variations in North Greenland Around 81°N Over the Last 6,000 Years

AbstractWe investigate full vector paleomagnetic changes recorded in high‐resolution sediments of Petermann Fjord, North Greenland, deposited over the last 6 kyr, in the context of the recent rapid changes in the geomagnetic field. A Paleomagnetic Secular Variation (PSV) stack (inclination, declination, and relative paleointensity) was reconstructed using four marine sediment cores with an independent age model constrained by seven radiocarbon ages. Magnetic investigations demonstrate that the paleomagnetic signal is carried by low coercivity ferrimagnetic minerals and is well reproduced in all cores, attesting to the quality and reliability of the paleomagnetic recording of these sediments. This signal is broadly consistent in directional changes with distant records in North America and the northern North Atlantic at centennial and millennial timescales, and has millennial scale intensity variations that are consistent with model predictions. The offset between a magnetization age determined through comparison with a northern North Atlantic PSV reference curve, GREENICE, and the radiocarbon age model indicates either a reasonable lock‐in depth of magnetization (∼11 cm from the coretop) or centennial‐scale reservoir age variation through time in the fjord. Reconstructed virtual geomagnetic pole (VGP) migration for the last 6 kyr shows that the recent migration of the magnetic North Pole is consistent with secular paleomagnetic variations on geologic timescales. Our results suggest that magnetic field intensity variations (temporal and spatial) are linked to magnetic flux lobe dynamics and influence the VGP migration.

Obtaining High‐Resolution Magnetic Records From Speleothems Using Magnetic Microscopy

AbstractSpeleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high‐resolution paleomagnetic records of short‐term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10−11 Am2), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm3, averaging tens to hundreds of years of magnetic variation. Nonetheless, smaller samples (∼1–10 mm3) can be measured using superconducting quantum interference device (SQUID) microscopy, with a sensitivity better than ∼10−15 Am2. To determine the application of SQUID microscopy for obtaining robust high‐resolution records from small‐volume speleothem samples, we analyzed three different stalagmites collected from Lapa dos Morcegos Cave (Portugal), Pau d'Alho Cave (Brazil), and Crevice Cave (United States). These stalagmites are representative of a range of magnetic properties and have been previously studied with conventional rock magnetometers. We show that by using SQUID microscopy we can achieve a five‐fold improvement in temporal resolution for samples with higher abundances of magnetic carriers (e.g., Pau d'Alho Cave and Lapa dos Morcegos Cave). In contrast, speleothems with low abundances of magnetic carriers (e.g., Crevice Cave) do not benefit from higher resolution analysis and are best analyzed using conventional rock magnetometers. Overall, by targeting speleothem samples with high concentrations of magnetic carriers we can increase the temporal resolution of magnetic records, setting the stage for resolving geomagnetic variations at short time scales.

The Added Value of Copper and Silver Metal from Printed Circuit Boards Waste Using Davis Tube with Variations of Size and Magnetic Intensity

The widespread use of electronic devices has led to a significant increase in electronic waste, including PCB (printed circuit board) waste. PCBs contain valuable metals like copper and silver, which can be reclaimed and reused. Recently, there has been a growing demand for urban mining processes to extract electronic waste PCB Flame Retardant-2 (FR-2) from laptops and computers. During the urban mining process, PCB FR-2 waste undergoes various physical treatments such as dismantling, crushing, and concentration processes. One of the concentration processes involves magnetic separation using a Davis tube. This study aims to investigate the effects of size and magnetic intensity variations on the recovery of copper and silver levels in FR-2 PCB waste. The magnetic concentration process was carried out using different size ranges (-63+100#, -100+150#, -150#) and magnetic intensities (1000 G, 2000 G, 3000 G). The results indicated that the most effective size for separating copper and silver is -63+100# and the optimal magnetic intensity is 1000 G. This resulted in copper and silver content of 45.66% and 0.162%, with recoveries of 80.135% and 62.505% respectively.

General properties of the response function in a class of solvable non-equilibrium models

Abstract We study the non-equilibrium response function $R_{ij}(t,t')$, namely the variation of the local magnetization $\langle S_i(t)\rangle$ on site $i$ at time $t$ as an effect of a perturbation applied at the earlier time $t'$ on site $j$, in a class of solvable spin models characterized by the vanishing of the so-called {\it asymmetry}.
This class encompasses both systems brought out of equilibrium by the variation of a thermodynamic control parameter, as after a temperature quench, or intrinsically out of equilibrium models with violation of detailed balance. The one-dimensional Ising model and the voter model (on an arbitrary graph) are prototypical examples of these two situations which are used here as guiding examples. Defining the fluctuation-dissipation ratio $X_{ij}(t,t')=\beta R_{ij}/(\partial G_{ij}/\partial t')$, where $G_{ij}(t,t')=\langle S_i(t)S_j(t')\rangle$ is the spin-spin correlation function and $\beta$ is a parameter regulating the strength of the perturbation (corresponding to the inverse temperature when detailed balance holds), we show that, in the quite general case of a kinetics obeying dynamical scaling, on equal sites this quantity has a universal form
$X_{ii}(t,t') = (t+t')/(2t)$, whereas $
\lim _{t\to \infty}X_{ij}(t,t')=1/2$ for any $ij$ couple. The specific case of voter models with long-range interactions is thoroughly discussed.

Effect of gamma and neutron irradiations on the physical, magnetic and electrical properties of Ni–Cu–Cd nano-ferrites

The physical, magnetic and electrical properties variations for the sol-gel auto combustion synthesized Ni0.3Cu0.2Cd0.5Fe2O4 by gamma (γ) and neutron irradiations dose applications are studied in this research. The irradiation have been done through 2.0 × 1011 and 1.9 × 1012 cm−2s−1 per min fast neutron flux and γ rays from the research reactor of TRIGA MARK-II and 64 KCi cylindrical 60Co source respectively within room temperature. The rate of 1 Mrad and 3 Mrad dose is 1.067 Mrad/h. XRD results show greater intensities for the irradiation doses. Due to the redistribution of ions, changes in the lattice constant have been found by the irradiation through the results of XRD and Rietveld Refinement process. The saturated magnetization obtained from the VSM is found to decrease first by the irradiation and then increase drastically. This analysis is performed by the popular pulse field technique of hysteresis loop for nano ferrites and further analyzed by LAS. The frequency dependent characteristics such as dielectric constant, electric modulus, impedance analysis and ac conductivity are inspected for all samples with both types of irradiation process. The electrical modulus Cole-Cole plots insure the dominant property as electric stiffness for investigated ferrties. Extreme decrease has been found in the dielectric natures which also show good agreement in the higher ac conductivity nature at the higher frequencies. Electrical parametric dependent overlapping two semicircles which are not complete have been found in the plots of Cole-Cole for impedance data. The energy of activation for the process of diffusion decreases by the irradiation.

Assessing soil erosion risk through geospatial analysis and magnetic susceptibility: A study in the Oued Ghiss dam watershed, Central Rif, Morocco

In northern Morocco, water erosion presents a critical risk for soil degradation and dam sedimentation, attributable to extreme climatic conditions, variegated topography, lithological vulnerabilities, and anthropogenic pressures. This study quantitatively and spatially evaluates soil erosion susceptibility within the catchment area of the Oued Ghiss dam in Central Rif, Morocco. Utilizing the Revised Universal Soil Loss Equation (RUSLE) integrated with Geographic Information Systems (GIS) and calibrated through magnetic susceptibility metrics, the study provides a detailed analysis of erosion factors. The model was applied using GIS to spatially analyze data on rainfall, soil type, topography, land cover, and management practices, with magnetic susceptibility measurements used to calibrate the model by identifying stable and erosion-prone areas. The resultant soil loss map reveals a mean erosion rate of 24 t/ha/year. Specifically, 37.28 % of the catchment area exhibits an erosion rate under 5 t/ha/year, 40.16 % between 5 and 10 t/ha/year, 22.77 % between 10 and 20 t/ha/year, and 0.86 % surpasses 20 t/ha/year. Magnetic susceptibility measurements across various soil profiles indicated that stable soils showed increased susceptibility towards the surface, while eroded soils displayed decreased susceptibility, with significant correlations found between magnetic susceptibility variations and the final risk map. This innovative calibration of the RUSLE model through magnetic susceptibility improves erosion vulnerability assessments and results in a more detailed soil loss map. The findings provide critical information for policymakers to develop targeted management plans for erosion-prone areas, particularly benefiting the Ghiss dam watershed, where these insights will aid in preventing dam siltation and enhancing water resource management. This confirms magnetic susceptibility's reliability in assessing soil erosion vulnerability and improving numerical models.

Detecting the Sigma Phase in Duplex Stainless Steel by Magnetic Noise and First Harmonic Analysis.

Non-destructive electromagnetic tests based on magnetic noise analysis have been developed to study, among others, residual stress, heat treatment outcomes, and harmful microstructures in terms of toughness. When subjected to thermal cycles above 550 °C, duplex stainless steels form an extremely hard and chromium-rich constituent that, if it is superior to 5%, compromises the steel's corrosion resistance and toughness. In the present work, a study was carried out concerning the interaction of excitation waves with duplex stainless steel. Hence, by analyzing the magnetic noise and variations in the amplitude of the first harmonic of the excitation waves, the detection of the deleterious sigma phase in SAF 2205 steel is studied. To simplify the test, a Hall effect sensor replaced the pick-up coil placed on the opposite surface of the excitation coil. Sinusoidal excitation waves of 5 Hz and 25 Hz with amplitudes ranging from 0.25 V to 9 V were applied to samples with different amounts of the sigma phase, and the microstructures were characterized by scanning electron microscopy. The results show that the best testing condition consists of applying waves with amplitudes from 1 V to 2 V and using the first harmonic amplitude. Thus, the test proved effective for detecting the formation of the deleterious sigma phase and can follow the ability to absorb energy by impact and, thus, the material embrittlement.

On the Role of Physical Processes in Controlling Equatorial Plasma Bubble Morphology

AbstractIn this study, we present the results of an analysis of the morphological features of Equatorial Plasma Bubbles (EPBs) over South America. In this context, we analyzed data from the Disturbance Ionosphere indeX (DIX) maps calculated using around 450 Global Navigation Satellite System (GNSS) stations. To mitigate the influence of magnetic disturbances on bubble development, only data from geomagnetically quiet days were utilized. This study covered the period from the post‐peak of solar cycle 24 (2015) to the pre‐peak of solar cycle 25 (2023), totaling 1321 nights with EPB occurrences, representing the largest data set of EPBs ever compiled for South America. Our analysis unveiled several key findings regarding EPBs and their behavior over the South American region. First, we observed that the amplitude of plasma depletions, as reflected in the DIX values, and the EPB latitudinal development follow an approximately 11‐year cycle driven by solar radiation levels. Furthermore, our analysis highlights the significant influence of factors such as the angle between the solar terminator and the magnetic meridian (T‐M angle), which varies inversely with the vertical plasma drift velocity during the pre‐reversal enhancement (PRE). Additionally, we discuss the longitudinal variations associated with magnetic declination, as well as the saturation behavior of EPB development with extreme solar flux.

Investigation of magnetic and electric properties of bismuth ferrite nanoparticles at different temperatures

Multiferroic bismuth ferrite shows a massive interest in its potential application in magnetic and electronic devices however maintaining high purity in bismuth ferrite nanoparticles at different temperatures is a difficult task for researchers. Several samples are prepared with different annealing temperatures and investigated in different atmospheres to recognize magnetic and electrical properties. A xerogel powder of bismuth ferrite is synthesized by the sol-gel route. The powder then anneals at 500, 600, 700, and 800 °C to form a nanostructure. X-ray diffraction analysis confirms that the annealed samples are in rhombohedral structure with R3c space symmetry and show a significant increase in crystal size and reduction in lattice strain with increasing annealing temperature. FESEM reveals the microstructural features of annealed nanoparticles which represent the conversion of spherical to cubic morphology with annealing temperature. Vibrating sample magnetometer investigations were conducted as a function of annealing and surface (300, 200, 80 K) temperatures. Insignificant variations of saturation magnetization are detected with surface temperature, but considerable degradation is observed with increasing annealing temperatures. The band-gap energy of bismuth ferrite nanoparticles annealed at 500, 600, 700, and 800 ºC is measured and significant escalation is observed from 1.93 to 2.06 eV. Electrical property analyses have been investigated as a function of frequency at different surface temperatures of 50, 100, 150, 200, 250, 300, and 350 °C. Remarkable variations are established in the electric and magnetic properties. Bismuth ferrite has been widely investigated due to its promising multifunctional device applications such as memory devices, spintronics, sensors, actuators, and photocatalytic and photovoltaic applications.

Delineation of deep-seated crustal structures from magnetic data in the southeastern part of the Niger Delta basin, Nigeria

Regional magnetic data in the southeastern segment of the Nigerian Niger Delta were evaluated with the aim of mapping deep-seated tectonic elements. Enhanced filtering operations and 3D forward modelling were applied on the magnetic data. These geologic features triggered the formation of rollover anticlines and faults that serve as structural traps in the study area. The filtered residual magnetic data revealed geologic structures characterized with NE - SW, N - S, and E - W orientations. The 3-D models detected the faulted crustal blocks, gradient zones, and intra-basement compositional magnetic variations. Furthermore, some prominent horst and graben structures as well as related normal faults characterized with distinct magnetic signatures were observed. Faults of base magnetic (of various compositions) were observed to be the fabricating mechanisms of the magnetic anomalies. Collectively, these structures influenced the patterns of magnetic anomalies with direct effects on the hydrocarbon trapping systems, as well as the pathways and accumulation zones for hydrothermal minerals. On the whole, the interpreted results revealed that the basement surface is rippling. Additionally, the depth result showed sedimentary thicknesses that ranged from 4–10 km. Again, the estimated crustal thickness varied from 14 to 19 km. This study has displayed the capabilities of the magnetic method in mapping the depth and configuration of basement rocks, which are crucial in controlling the formation of structural traps. Identifying these basement structures early helps in understanding the overall geological framework and potential hydrocarbon systems.

Accelerated discovery of multi-property optimized Fe–Cu alloys

The next generation of rotating electrical machines requires materials with an optimized combination of magnetic, electrical and mechanical properties. High-throughput experiments can accelerate the discovery of relevant materials. Past work has focused on complex multicomponent alloys in which it is difficult to pinpoint the effect of each component. On the other hand, in this work, Fe–Cu binary alloys were used as a model materials system to determine the feasibility of novel materials discovery through a rapid determination of multiple properties. The microstructures, magnetic, electrical, and mechanical properties of Fe–Cu alloys were rapidly determined. With increasing Cu content in Fe-xCu from 0 to 40 wt.%, the phases present changed from single phase BCC to a two-phase FCC + BCC microstructure. There was a decline in the saturation magnetization (Ms) from 211.3 to 118 emu/g. The hardness value increased from 166.3 HV to 238.5 HV, the coercivity (Hc) ranged from 14.6 to 45.7 Oe, and the resistivity varied between 27.3 and 43.0 μΩ·cm. The increased content of a Cu-rich phase led to a decrease in Ms and grain size, and higher Hc and hardness. Using an accelerated methodology, a significant variation in material properties was determined. Three compositions, i.e., Fe–3Cu, Fe–4Cu and Fe–10Cu, with a good balance of properties were identified for potential use in energy applications.

Оценки положения Северного магнитного полюса в 2021 году

Based on measurements of magnetic declinations with standard shipboard instruments in three marine expeditions in the Russian Arctic, estimates of the Earth`s North Magnetic Pole position in 2021 were obtained. It is located in the Russian sector of the Arctic. Experiments on determining the North Magnetic Pole in 2021 were carried out on board the research vessels “Professor Molchanov” and the scientific expedition one “Mikhail Somov” supported by the hydrographic ship of “Horizon”. The calculations used a comparison of measurements along the quasi-closed route with magnetic declination data using the International Geomagnetic Analytical Field IGRF13 (International Geomagnetic Reference Field) model with the choice of the minimum discrepancy, a simple inverse matching problem for smooth functions was solved. The results obtained confirm the possibility of regular operational assessment of the Earth`s magnetic poles position. The technology of assessing the magnetic deviation of ships is considered

Ni thin-films on Pd surfaces and effects of oxygen adsorption: Ab-initio study of structures, electronic properties, magnetic anisotropy

We report first-principles electronic structure calculations of the structural, electronic, and magnetic properties of model epitaxial layers consisting of nickel (Ni) atomic layers deposited on palladium (Pd) substrate, i.e., Ni(001)m∣Pd(001)n where m=1,2,6 and n=3,10, are layer thicknesses. We also investigate the effect of oxygen adsorption on the calculated properties. We found variation in magnetization of between ≈0.6μB to 1.00 μB across the nickel layers. Also, finite magnetic moments albeit of small values of between 0.2 μB and 0.3 μB is found on the Pd at the interface. This magnetic moment on an otherwise non-magnetic Pd atoms has been adduced to interfacial strain due to lattice mismatch between the Ni and Pd layers at the Ni|Pd interface. The effect of adsorbed oxygen on the Nim∣Pdn is that it increases the magnetic moment on the nickel layers. Also, regarding the magnitude of magnetic anisotropy energy (MAE), we found a high perpendicular values of 1.63 meV and 1.37 meV per unit cell respectively for Nim∣Pd10 (m=2,6) which are relatively higher than those reported for other transition metal epitaxial layers. However, the presence of oxygen atom on the Ni∣Pd changes the direction and magnitude of MAE. Indeed, O adsorption favours or enhances in-plane magnetization direction depending on the thickness of the Ni layers for a fixed Pd thickness. Plots of local density of states (LDOS) which include the effect of spin–orbit coupling (SOC), show that in the case of Ni∣Pd having perpendicular MAE, there appears a new SOC-induced electronic states below and above the Fermi level. These states appears to stabilize this type of magnetic anisotropy. On the other hand, in-plane MAE is characterized by SOC-induced localized states below the Fermi level (EF) as well as the lowering of the DOS at the EF. Our work explores the physical, magnetic and electronic properties that may be useful in designing Ni∣Pd-based superlattices for magnetic or spintronic applications.

Multiferroic properties of NiFe2O4-Ba0.7Ca0.3TiO3 nanocomposites

In this report, we present results on the multiferroic properties of four nanocomposite samples of NiFe2O4-Ba0.7Ca0.3TiO3 (NFO/BCTO), which were fabricated through combinations of high-energy ball milling, heat treatment, and spark plasma sintering techniques. Structural analyses revealed that these samples simultaneously contain two phases of nano-sized NiFe2O4 (NFO) and Ba0.7Ca0.3TiO3 (BCTO) crystals. The addition of NFO into the BCTO-host did not alter the crystal structure but significantly improved the multiferroic characteristics compared to pure BCTO. Furthermore, variations in saturation magnetization (M s) and coercivity (H c) were investigated as a function of temperature. The results showed that Ms increased gradually with the concentration of NFO. In terms of temperature dependence, M s(T) data deviated from the Bloch’s law with an exponent coefficient α changing in the range of 1.8–1.9, decreasing gradually as the NFO concentration increased. Meanwhile, H c decreased gradually as the NFO concentration increased and followed the Kneller’s law in terms of temperature dependence.