Magnetic Susceptibility Curves Research Articles

Nature-based solutions for monitoring the impact of vehicular particulate matter and for the preventive conservation of the Palatine Hill archaeological site in Rome, Italy

Magnetic and chemical biomonitoring methodologies were applied to the southern slopes of the Palatine Hill archaeological area in Rome, Italy. Plant leaves and lichen transplants were respectively sampled and exposed between July 2022 and June 2023 to assess the impact of vehicular particulate matter from Via dei Cerchi, a trafficked road coasting Circus Maximus, towards the archaeological area upon the Palatine Hill. The magnetic properties of leaves and lichens, inferred from magnetic susceptibility, hysteresis loops and first order reversal curves, were combined with the concentration of trace elements. It was demonstrated that the bioaccumulation of magnetite-like particles, associated with tracers of vehicular emissions, such as Ba and Sb, decreased with longitudinal distance from the road, without any important influence of elevation from the ground. Lichens demonstrated to be more efficient biomonitors of airborne PM than leaves, irrespective of the plant species. Conversely, leaves intercepted and accumulated all PM fractions, including road dusts and resuspended soil particles. Thus, plant leaves are suitable for providing preventive conservation services that limit the impact of particulate pollution on cultural heritage sites within busy metropolitan contexts.

Structural and magnetic transformations in the system YBaCo4O7+X (x = 0, 0.1, 0.2)

The modification of magnetic and elastic properties of YBaCo4O7+x (x = 0, 0.1) cobaltite series at a small controlled deviation x = 0, 0.1, 0.2 from stoichiometry has been investigated. The non-stoichiometric cobaltites with x > 0.1 are found to be separated into two structural phases with different values of x under certain synthesis and heat-treatment conditions of the YBaCo4O7+x system (x = 0, 0.1, 0.2). A non-trivial magnetic behavior is observed in stoichiometric YBaCo4O7. Magnetic moment ΔM = MFC–MZFC induced by an external magnetic field (an analog of thermo-residual magnetization) exhibits anomalies at magnetic phase transition temperatures TN1 and TN2 that coincide with Young’s modulus anomalies. Conversely, in the magnetic susceptibility curves taken in the FC and ZFC modes, phase transitions are not discerned. When x deviates from stoichiometry, the ratio between two magnetic ions Co3+/Co2+ changes, the induced moment ΔM increases, and a residual ferromagnetic moment of ∼ 10-2μB appears in the magnetization curves at low temperatures. At a slight deviation from the oxygen stoichiometry in the samples, the structural distortion disappears, and the anomalies in the elastic characteristics near the TN region rapidly diffuse and vanish. It has been found that when YBaCo4O7+x cobaltites deviate from stoichiometry, the evolution of their magnetic properties is similar to that observed at the transition from Y-based to Ca-based cobaltite. Two scenarios of the cobalt subsystem magnetic behavior with an increasing fraction of cobalt Co3+ ions have been discussed.

Stress-induced changes in magnetite: insights from a numerical analysis of the Verwey transition

SUMMARY Magnetic susceptibility behaviour around the Verwey transition of magnetite (≈125 K) is known to be sensitive to stress, composition and oxidation. From the isotropic point (≈130 K) to room temperature, decreasing magnetic susceptibility indicates an increase in magnetocrystalline anisotropy. In this study, we present a model which numerically analyses low-temperature magnetic susceptibility curves (80–280 K) of an experimentally shocked (up to 30 GPa) and later heated (973 K) magnetite ore. To quantify variations of the transition shape caused by both shock and heating, the model statistically describes local variations in the Verwey transition temperature within bulk magnetite. For the description, Voigt profiles are used, which indicate variations between a Gaussian and a Lorentzian character. These changes are generally interpreted as variations in the degree of correlation between observed events, that is between local transition temperatures in the model. Shock pressures exceeding the Hugoniot elastic limit of magnetite ($ \ge $5 GPa) cause an increase in transition width and Verwey transition temperature, which is partially recovered by heat treatment. Above the Verwey transition temperature, susceptibility variations related to the magnetocrystalline anisotropy are described with an exponential approach. The room temperature magnetic susceptibility relative to the maximum near the isotropic point is reduced after shock, which is related to grain size reduction. Since significant oxidation and cation substitution can be excluded for the studied samples, variations are only attributed to changes in elastic strain associated with shock-induced deformation and annealing due to heat treatment. The shocked magnetite shows a high correlation between local transition temperatures which is reduced by heat treatment. The model allows a quantitative description of low-temperature magnetic susceptibility curves of experimentally shocked and subsequently heat-treated polycrystalline magnetite around the Verwey transition temperature. The curves are accurately reproduced within the experimental uncertainties. Further applications for analysing magnetite-bearing rocks seem possible if model parameters, such as for oxidation are included into the model.

A cryogenic magnetic refrigerant: Magnetocaloric study of EuB2O4 compound

Adiabatic demagnetization refrigeration (ADR) technology has the advantage of not relying on helium-3 resources and gravity compared to traditional ultra-low temperature refrigeration technology. The key to the development of ADR technology is finding magnetic refrigeration materials with brilliant magnetocaloric properties. In this study, polycrystalline EuB2O4 was successfully prepared by solid-phase reaction method. The analysis of magnetic susceptibility curves and first-principles calculations reveals a magnetic phase transition from antiferromagnetic (AFM) to paramagnetic (PM) of EuB2O4, with TN = 0.72 K. The magnetic entropy change (-ΔSM) is evaluated up to 5 T, with the maximum value of 19.4 J·kg−1K−1 (88.7 mJ·cm−3K−1), 35.0 J·kg−1K−1 (160.0 mJ·cm−3K−1) and 50.8 J·kg−1K−1 (232.2 mJ·cm−3K−1) at around T = 1.3 K and under μ0ΔH = 1 T, 2 T and 5 T, respectively, which were significantly higher than those of the commercial magnetic refrigerant Gd3Ga5O12. The large -ΔSM suggest that EuB2O4 is a potentially great magnetic refrigerant for obtaining ultra-low temperature.

Field-induced Bose–Einstein condensation in zigzag spin chain KGaCu(PO4)2

Single crystals of GaKCu(PO4)2 were synthesized using the hydrothermal method, and subsequent measurements of specific heat, magnetic susceptibility, and high-field magnetization were performed. A broad peak is observed in the magnetic susceptibility and specific heat curves, with the maximum values appearing at about 11.5 K and 5.29 K, respectively. The highest maximum peak value of susceptibility is observed when the magnetic field is applied along the c-axis, followed by the a-axis, b-axis, and polycrystalline samples. These indicate that the system exhibits one-dimensional magnetism and the magnetic easy axis is the c axis. The magnetization at 2 K reveals the occurrence of a field-induced Bose–Einstein condensation (BEC) phase within the magnetic field range of approximately 8−12 T. High-field magnetization up to 40 T indicates that the compound reaches magnetization saturation as the field exceeds H s = 12 T. Through systematic measurements, a field-temperature (H−T) phase diagram was constructed, and dome-like phase boundaries were observed. The findings suggest that GaKCu(PO4)2 is a spin gap system and a promising candidate for studying BEC of magnons due to its phase transition boundary occurring at low magnetic fields.

Magnetic training of the soft magnetorheological elastomers

The effect of repetitive quasi-static magnetisation of a magnetorheological elastomer on its magnetic response is discussed. Typical components of this material, namely soft silicone rubber and carbonyl iron powder, are used to produce magnetically sensitive composite samples. The composite specimens are examined by vibrating sample magnetometry. The influence of the elasticity of the composite matrix on the change in magnetic differential susceptibility of the material as a function of the number of repeated magnetisation cycles is evaluated. The soft matrix elastomers are characterised by the presence of maxima in the initial part of the differential susceptibility curves. The sample magnetisation values corresponding to such maxima vary with the number of magnetisation cycles. In addition, the initial magnetic susceptibility curves of soft samples obtained at different polarity of the applied field are not symmetrical. Symmetry is obtained by performing several subsequent magnetisation cycles. The differential susceptibility curves are affected by both reversible and irreversible processes related to particle mobility in the matrix. The magnetic response of composite samples with rigid matrices is more similar to that of classical soft magnetic materials.

Enantiomeric Complexes Based on Ruthenium(III) and 2,2'-Biimidazole: X-ray Structure and Magnetic Properties.

We have prepared and characterized two Ru(III) compounds based on the 2,2'-biimidazole (H2biim) ligand, namely, a single complex of formula cis-[RuCl2(H2biim)2]Cl·4H2O (1) and a racemic mixture of formula {cis-[RuCl2(H2biim)2]Cl}2·4H2O (2), which contains 50% of Ru(III) complex 1. Both compounds crystallize in the monoclinic system with space groups C2 and P21 for 1 and 2, respectively. These complexes exhibit the metal ion bonded to four nitrogen atoms from two H2biim molecules and two chloride ions, which balance part of the positive charges in a distorted octahedral geometry. Significant differences are observed in their crystal packing, which leads to the observation of differences in their respective magnetic behaviors. Despite having imidazole rings in both compounds, π-π stacking interactions occur only in the crystal structure of 2, and the shortest intermolecular Ru···Ru separation in 2 is consequently shorter than that in 1. Variable-temperature dc magnetic susceptibility measurements performed on polycrystalline samples of 1 and 2 reveal different magnetic behaviors at low temperatures: while 1 behaves pretty much as a magnetically isolated mononuclear Ru(III) complex with S = 1/2, 2 exhibits the behavior of an antiferromagnetically coupled system with S = 0 and a maximum in the magnetic susceptibility curve at approximately 3.0 K.

Revival of Ferromagnetic-Metallic Phase and Emergence of Griffiths Phase via Ni and Cr Substitution in Charged-Ordered Pr0.75Na0.25MnO3 Manganite

Polycrystalline samples of Pr0.75Na0.25Mn1-xAxO3 (A = Ni, Cr; x = 0, 0.03) were prepared using conventional solid-state method and their structural and magnetic properties were investigated. Monovalent-doped Pr0.75Na0.25MnO3 exhibits insulating behavior which is related to the strong localization of charge carriers due to the presence of charge ordering (CO). The substitution of different types of magnetic ions, A, which are Ni2+ and Cr3+, at a concentration of x = 0.03 at the Mn site in the CO Pr0.75Na0.25Mn1-xAxO3 manganite, has been found to dramatically modify its structural and magnetic properties. X-ray diffraction patterns showed that all samples were present in single phase and crystallized in orthorhombic structure with Pnma space group. The Rietveld refinement analysis showed that the unit cell volume increased due to Ni2+ substitution, while it decreased due to Cr3+ substitution, which may be attributed to the different ionic radii of both ions. The suppression of the CO state and the induction of the ferromagnetic-metallic state in the Ni-substituted and Cr-substituted samples are suggested to be due to the induction of double-exchange interaction involving Ni2+–O–Mn4+ and Mn3+–O–Cr3+, respectively. The variation in magnetic properties between the Ni-substituted and Cr-substituted samples is suggested to be due to the existence of different strengths of ferromagnetic interaction between Ni2+–O–Mn4+ and Mn3+–O–Cr3+. In addition, the deviation of the temperature dependence of the inverse magnetic susceptibility curves from the Curie-Weiss law suggests the existence of Griffith’s phase-like behaviour for both substitution samples. The Ni-substituted sample induced a greater GP effect than the Cr-substituted sample due to the larger difference of TC and TG value (TC-TG).

Possible evidence for geomagnetic intensity anomaly around 5500 BP from archaeomagnetic analyses of San Jacinto pottery, Caribbean Colombia

San Jacinto archaeological site in Northern Colombia hosts America's oldest pottery, radiometrically dated between 5940 ± 60 BP and 5190 ± 40 BP. Eleven ceramic fragments were subjected to detailed archaeomagnetic and archaeointensity investigation. Alternating field and thermal demagnetization, as well as magnetic mineralogy experiments, were carried out before double heating paleointensity determination to select the most suitable samples. Magnetic susceptibility vs. temperature curves revealed that magnetite and hematite grains are the main carriers of the thermoremanent magnetization. However, the contribution of hematite in total remanence seems to be negligible. Thirty-six samples corresponding to six pottery fragments were selected for Thellier-type paleointensity determinations. Mean intensity values range from 50.7 ± 4.7 to 65.3 ± 11.9 μT while virtual Axial Dipole Moments vary from 12.6 ± 1.2 to 16.2 ± 2.9 × 1022 Am2, indicating high geomagnetic field strength compared to values predicted by global geomagnetic models. This represents the first evidence of relatively high archaeointesities before 1000 BC. Similar or even higher geomagnetic strengths are observed in the Levant around 1100–800 BC and SW Pacific Region at 1450 AD. The actual cause of such anomalously high intensity, often attributed to the processes in the vicinity of the Core-Mantle Boundary, is still not fully understood.

Effects of the Sr/Ba and Eu2+/Eu3+/Dy3+ ions content on the luminescent emission of M0.90Eu0.1‐xDyxZr4(PO4)6 nanophosphors with M = Sr or Ba and x = 0, 0.025, 0.050 and 0.075

The preparation and study of new pure M0.90Eu0.1‐xDyxZr4(PO4)6 samples with M = Sr or Ba and x = 0, 0.025, 0.050 and 0.075 was described here in detail. Currently, the luminescent emission study of this type of samples based on their tunable with the type and content of ions in the host lattice is the subject of research. These samples were synthesized by a combustion route with urea addition, followed by treatment in a reducing N2/H2 atmosphere. The effect of the strontium by barium substitution and the europium by dysprosium partial substitution on the structure, powder morphology, luminescent emission and magnetic behavior was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy and magnetic measurements. X-ray diffraction patterns of the pure samples show diffraction maxima that can be assigned to a rhombohedral symmetry of space group R-3 with Z=6, compatible with a NASICON-type structure. FTIR spectra of the investigated samples show a broad band assignable to the different vibrational modes of the PO43- groups. The experimental FTIR study was complemented with a theoretical study based on the SrZr4(PO4)6 structure and using different DFT methods and basis sets. Highly agglomerated spherical nanoparticles with an average particle size of about 18 nm that slightly increased with dysprosium content were found in TEM images. Broad emission bands were observed in the PL spectra of obtained samples, related to both the strontium by barium substitution and the different Eu2+/Eu3+/Dy3+ content. Magnetic susceptibility curves as a function of temperature confirm the presence of Eu2+ ions in Sr0.90Eu0.1Zr4(PO4)6 sample, and of Dy3+ ions with different Eu2+/Eu3+ ions content in the remaining M0.90Eu0.1‐xDyxZr4(PO4)6 samples.

Exploration of low field magnetic states in NdCe x CrO3

We report the structural and magnetic properties of NdCe x CrO3 () single-phase samples to classify the influence of Ce substitution on the Nd-site. The electron density profile indicates the possible covalent nature of Cr–O bonds. The x-ray photoelectron spectroscopy confirms a mixed Ce valency with a constant ratio of Ce3+/Ce4+ ions in all substituted compounds and the charge neutralization through the oxygen vacancies. The magnetization measurements reveal an increase in antiferromagnetic ordering temperature () and spin-reorientation transition temperature () and unfold soft spin-reorientation attributed to diluted superexchange interactions upon Ce incorporation. The presence of mixed Ce ions induces the merging of the hysteresis loop with a significant exchange bias (EB) field. We demonstrate for the first time that the magnitude of the magnetization is different for the same applied field in positive and negative directions, indicating the existence of two different magnetic states. The difference between these two magnetic states possibly arises from the pinning of Cr3+ spins, which requires an additional Zeeman energy for it to rotate. This maximum Zeeman energy from the normalized magnetic susceptibility vs. temperature curves correlates with the maximum EB field, validating unusual EB in these compounds.

Magnetic properties of the quasicrystal approximant Au65Ga21Tb14

The magnetic properties of the quasicrystal approximant ${\mathrm{Au}}_{65}{\mathrm{Ga}}_{21}{\mathrm{Tb}}_{14}$ were investigated using magnetization and neutron diffraction experiments. The temperature dependences of the magnetic susceptibility and magnetization curve indicate dominant ferromagnetic interactions, whereas a whirling antiferromagnetic order was observed in neutron diffraction experiments. In the antiferromagnetic phase, the magnetic moments are aligned almost perpendicular to a pseudofivefold symmetry axis, which corresponds to the easy-axis direction of a Tb atom. Magnetic properties similar to those of ${\mathrm{Au}}_{72}{\mathrm{Al}}_{14}{\mathrm{Tb}}_{14}$ in spite of the substantial difference in the Au concentration suggest the robustness of the easy-axis anisotropy against the chemical environment.

Evolution of the Earth's magnetic field strength in northwestern Argentina during the last two millennia: Towards the improvement of south American geomagnetic paleosecular variation curve

A magnetic mineralogy and absolute geomagnetic intensity study was carried out on prehispanic ceramic fragments from the Southern Andes region (Northwest Argentina). Magnetic susceptibility vs. temperature curves and alternating field demagnetization treatments were applied to select the most suitable samples for the absolute archaeointensity experiments. A total of 66 samples were analyzed following the Thellier modified by Coe protocol, including cooling rate corrections and potential mitigation of the magnetic anisotropy effect. Thirty-eight samples (out of 66) belonging to nine pottery fragments yielded reliable absolute intensity determinations The new data, accompanied by associated radiocarbon ages, were integrated into previously published data in order to construct an improved paleosecular variation curve for South America. The highest quality data covers only the last 1000 years. The general variation patterns show good agreement with global geomagnetic prediction models. This updated regional curve may be used as the reference curve for archaeomagnetic dating in the major part of South America (Brazil, Argentina, Chile, Uruguay and Bolivia), even though caution should be paid for the areas and time periods poorly covered by data.

Reversible Thermal Hysteresis in Heating‐Cooling Cycles of Magnetic Susceptibility: A Fine Particle Effect of Magnetite

AbstractThermomagnetic curves of magnetic susceptibility (κ) are key to characterizing magnetic properties. We report hump‐shaped κ‐T curves of magnetite‐bearing basalt during heating‐cooling cycles to ∼340°C, with a large thermal hysteresis and similar starting and ending values, even in multiple repeated cycles, ruling out changes in magnetic mineralogy. Based on FORC diagrams and published results of engineered materials, we propose that thermal hysteresis arises from configurations of magnetic moments in clusters of single‐domain particles due to dipolar coupling, with different collective behavior during heating and cooling. This effect modifies the hump‐shaped thermal relaxation behavior of the individual nanoparticles. FORC and κ‐T results indicate an increase in effective particle sizes after 700°C‐heating. Our results are a warning against premature interpretation of a decreasing trend in κ‐T curves by maghemite inversion. Instead, fine particle behavior should be considered when a hump‐shaped κ‐T behavior is detected.

The influence of off-centre donor impurity on the tuning of the quantum ring magnetic susceptibility

The 1/N expansion method has been used to investigate the problem of an electron moving in a two-dimensional semiconductor quantum ring with an off-center impurity. The energy spectra, magnetization, and magnetic susceptibility have been calculated as a function of the magnetic field, impurity position, temperature, and quantum ring parameters. Interesting energy-level crossings attributed to QR confinement manifest themselves as low-temperature oscillations in the magnetization and magnetic susceptibility curves. On the contrary, the presence of impurity at the QR center eliminates these level crossings. This work shows that changing the impurity position can manipulate the magnetic field value correspondence to these diamagnetic-paramagnetic phase transitions.

Antiferromagnetism of CeCd0.67As2 existing deep inside the narrow gap semiconducting state

Single crystals of $R$Cd$_{0.67}$As$_2$ ($R$ = La and Ce) have been synthesized by high temperature ternary melt and their physical properties have been explored by means of magnetization, specific heat, electrical resistivity, Hall coefficient, and thermoelectric power measurements. $R$Cd$_{0.67}$As$_2$ compounds indicate a (structural) phase transition at high temperatures, accompanied by a remarkable increase of the electrical resistivity with an extremely low carrier concentration. CeCd$_{0.67}$As$_2$ exhibits a large magnetic anisotropy and an antiferromagnetic (AFM) order below $T_{N} = 4$~K. Magnetic susceptibility curves, together with magnetization isotherms and specific heat, are analyzed by the point charge model of crystalline electric field (CEF). In the paramagnetic state, the observed magnetic properties can be well explained by the CEF effects, implying that the 4$f$ moments remain localized. Electrical resistivity measurements, together with Hall resistivity and thermoelectric power, also suggest highly localized 4$f$ electrons, where Kondo contributions are negligible. The low temperature physical properties manifest strong magnetic field dependencies. For $H \perp c$, $T_{N}$ shifts to lower temperature as magnetic field increases, and eventually disappears at $H_{c} \sim 60$~ kOe. Inside the AFM state, three metamagnetic transitions are clearly evidenced from the magnetization isotherms. The RKKY interaction may be responsible for the AFM ordering in CeCd$_{0.67}$As$_2$, however it would have to be mediated by extremely low charge carriers. Although the AFM ordering temperature in CeCd$_{0.67}$As$_2$ can be continuously suppressed to zero, no AFM quantum phase transition is expected due to the lack of conduction electron clouds to screen the 4$f$ moments.

Influence of crystalline electric field on the magnetic properties of CeCd3X3(X=P,As)

CeCd$_3$P$_3$ and CeCd$_3$As$_3$ compounds adopt the hexagonal ScAl$_3$C$_3$-type structure, where magnetic Ce ions on a triangular lattice order antiferromagnetically below $T_\text{N} \sim$0.42~K. Their crystalline electric field (CEF) level scheme has been determined by fitting magnetic susceptibility curves, magnetization isotherms, and Schottky anomalies in specific heat. The calculated results, incorporating the CEF excitation, Zeeman splitting, and molecular field, are in good agreement with the experimental data. The CEF model, with Ce$^{3+}$ ions in a trigonal symmetry, explains the strong easy-plane magnetic anisotropy that has been observed in this family of materials. A detailed examination of the CEF parameters suggests that the fourth order CEF parameter $B_{4}^{3}$ is responsible for the strong CEF induced magnetocrystalline anisotropy, with a large $ab$-plane moment and a small $c$-axis moment. The reliability of our CEF analysis is assessed by comparing the current study with earlier reports of CeCd$_{3}$As$_{3}$. For both CeCd$_{3}X_{3}$ ($X$ = P and As) compounds, less than 40 \% of $R\ln(2)$ magnetic entropy is recovered by $T_\text{N}$ and full $R\ln(2)$ entropy is achieved at the Weiss temperature $\theta_{p}$. Although the observed magnetic entropy is reminiscent of delocalized 4$f$-electron magnetism with significant Kondo screening, the electrical resistivity of these compounds follows a typical metallic behavior. Measurements of thermoelectric power further validate the absence of Kondo contribution in CeCd$_{3}X_{3}$.

KMB4O6F3 (M = Co, Fe): two-dimensional magnetic fluorooxoborates with triangular lattices directed by triangular BO3 units.

Frustrated magnetic systems are of great interest owing to their spin liquid state for application in quantum computing. However, experimentally, spin liquid has not been realized. Thus, experimental explorations of frustrated magnetic systems including triangular lattices are still urgent, particularly for directed synthesis compared to random exploration. Herein, for the first time, directed by the use of a triangular unit of the BO3 anion group, two novel layered magnetic fluorooxoborates KMB4O6F3 (M = Co 1, Fe 2) with triangular lattices have been hydrothermally synthesized and characterized. Compounds 1 and 2 are isostructural and crystallize in the P21/c space group with layered magnetic triangular lattices, which are further separated by K+ ions. Magnetic susceptibility curves of both 1 and 2 show no λ-anomaly peak down to a low temperature of 2 K in the absence of a magnetic long-range ordering transition, which are further confirmed by the heat capacity results. The magnetic-field dependence of magnetization at 2 K shows saturation of 2.20μB for 1 and 4.24μB for 2, respectively, at 7 T, after roughly subtracting the Van Vleck paramagnetic contribution. Further in-depth investigation of the underlying physics at a lower temperature below 2 K would be subsequently performed. Moreover, thermal stability and FT-IR and UV-vis-NIR spectroscopy with optical bandgap properties are also reported. Most importantly, our work provides a promising method to experimentally realize specific magnetic lattices (e.g. triangular lattices) directed by the use of triangular groups (e.g. BO3) as the functional unit.

A new Ruddlesden-Popper oxide LaSr3Mn1.5Fe1.5O9.71 as photocatalyst for degrading highly toxic dyes in waste water: Structural, magnetic and transport properties

This paper presents the magnetic, transport, and photo-catalytic properties of a new Sr4Ti3O10-type oxygen deficient Ruddlesden-Popper oxide LaSr3Mn1.5Fe1.5O9.71. The Rietveld refinement analysis of the PXRD data confirms the formation of the compound which crystallizes in tetragonal symmetry and adopts space group I4/mmm, tI34. The phase is found to be oxygen deficient as determined from the results of iodometric titrations. The energy band gap (Eg) obtained from the DRS study shows that the phase is semiconducting in nature at room temperature. The magnetic studies revealed that the oxygen deficient phase exhibits dominant anti-ferromagnetic (AFM) ordering with Néel temperature, TN ​= ​71 ​K owing to Fe3+―O―Fe3+, Mn4+―O―Mn4+ super-exchange interactions. The divergence between the zero field cooled (ZFC) and field cooled (FC) molar magnetic susceptibility curves at low temperatures implies that the phase shows a spin-glass transition. The temperature-dependent resistivity measurements indicate that the material exhibits insulating behavior with decreasing temperature. The conduction mechanism is discussed by fitting the resistivity data in different transport mechanism models. It has been found that the conduction mechanism is dominated by Mott’s variable range hopping model. The photo-oxidative degradation of different dye pollutants using LaSr3Mn1.5Fe1.5O9.71 as a photocatalyst was carried out under visible irradiation. The results indicate that Methylene Blue (MB) shows 99.1% degradation in 45 ​min while Rhodamine B (RhB) and Methyl Orange (MO) dyes show 99.3% and 98.6% degradation respectively in 20 ​min.

Prediction of magnetic properties of a single-molecule magnetic metallofullerene cluster DySc2N@C80

In this work, we proposed a particle swarm optimization algorithm combined with Monte Carlo simulation method to investigate the magnetic properties of a single-molecule magnetic metallofullerene cluster DySc2N@C80. Based on the experimental results, we estimated the values of the exchange coupling and the anisotropy of the present system according to the critical temperature TC, which achieved a good agreement between simulated and experimental results. In addition, we also obtained the influence of size effect, the curves of magnetization, magnetic susceptibility and internal energy induced by external magnetic field and hysteresis behaviors at different temperatures.