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Structural, electrical and magnetic features of Kagomé YBaCo4O7 system

and 8 T fields. In Table 1 the calculated values for T 0 and N(E F ) are also reported. The typical value of T 0 and N(E F ) are about 3.4 × 10 8 K and 2.4 × 10 17 eV −1 cm −3 , respectively. 3.5 Magnetization The DC magnetic susceptibility (M/H) measurements for YBaCo 4 O 7 were carried out by using SQUID magnetometer as shown in Fig. 6 . In this paper, we have shown the magnetization of YBaCo 4 O 7 compound measured at 1 Tesla (T) magnetic field. From 80 K to 300 K, the data do not obey a Curie-Weiss relationship. We have collected our data for

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Formation of Fe and Ni substituted LiMn2–XMXO4 nanopowders and their crystal and electronic structure and magnetic properties

line is clearly visible in the spectrum. For these lines, the background individually selected in the region limited to the particular line is subtracted and after that integration of the peak area is performed [ 56 ]. The Gaussian-Lorentzian functions were used to fit the XPS core level spectra. Magnetic susceptibility was measured using the SQUID Magnetometer MPMS-XL-7AC (Quantum Design) in the temperature range of 2 K to 400 K. The 57 Fe Mössbauer spectrum was recorded at room temperature using a constant acceleration spectrometer with 57 Co:Cr source. The

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High resolution airborne radiometric and magnetic studies of ilesha and its environs, southwestern Nigeria

wavenumber methods, Society of Exploration Geophysics Annual General Meeting, Calgary, Alberta, Expanded Abstracts. [44] Olowofela, J.A., Badmus, B.S., Ganiyu, S.A., Olurin, O.T., Babatunde, P. (2011): Source location and depth estimation from digitised aeromagnetic data acquired from the basement complex formation. Earth Science India , 4, pp. 136–142. [45] Geosoft INC. (2010). Geosoft INC. 85 Richmond Street, 8 th Floor, Toronto, Ontario, Canada. [46] Frantisek, H., Jiri, P., Jazek, J. Chadina, M. (2009): Out – of-Phase Magnetic Susceptibility of

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Magnetic characterization of microcrystalline Na3Ln0.99–xEr0.01Crx(PO4)2 orthophosphates synthesized by Pechini method (Ln = La, Gd)

Abstract

Na3Ln(PO4)2 orthophosphates (Ln = La, Gd) doped with Er3+ and co-doped with Cr3+ ions were synthesized by Pechini method and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. Low temperature EPR spectra were detected and analyzed in terms of temperature dependence and the structure of the obtained materials. They show that erbium and chromium ions substitute Ln3+ and also Na+ ions or Na+ channels forming complex EPR spectra. Both kinds of ions reveal ferromagnetic type of interaction which shows some anomaly at the temperature between 10 K and 15 K. Magnetic susceptibility reveals a weak antiferromagnetic kind of interaction dominating in the whole temperature range, from 3.5 to 300 K.

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Study of magnetic properties of two samples from FeVO4-Co3V2O8 system

Abstract

Two samples containing phases formed in the FeVO4-Co3V2O8 system were prepared by a conventional sintering method. The sample designated as H5 was one-phase with the howardevansite-type structure, while the sample designated as HL7 contained a mixture of H-type and lyonsite-type structures. The temperature dependence of the electron paramagnetic resonance (EPR) spectra and static magnetic susceptibility χ was investigated in the temperature range from liquid helium to room temperature. Both the EPR spectra and the dc magnetic susceptibility showed anomalous behavior indicating that the magnetic competition process may be responsible. A comparison of the obtained results with previous studies on related compounds with the same structure, i.e. M3Fe4V6O24 (M = Mg(II), Zn(II), and Cu(II)) revealed that the observed anomaly shifted to lower temperatures on replacing the non-magnetic ions by magnetic Co(II) ions. The temperature dependence of the inverse susceptibility χ −1 indicates the existence of antiferromagnetic interactions between Fe(III) and Co(II) spins in sample H5. The obtained values of the Curie-Weiss temperatures are lower than for the Mn3Fe4V6O24 compound and comparable to compounds from M3Fe4V6O24 systems with M diamagnetic cations. The introduction of cobalt cations intensifies the magnetic frustration what is reflected in the temperature dependence of the magnetic susceptibility at low temperatures.

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Solvothermal synthesis and magnetic properties of β-Co2P nanorods

Abstract

Hexagonal high temperature phase β-Co2P nanorods with a diameter of around 50 nm were synthesized via a mild solvothermal route. The reaction was carried out at 180 °C using cobalt chloride hexahydrate (CoCl2 · 6H2O) as Co source and yellow phosphorous as P source. The composition, structure as well as morphology were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and transmission electron microscopy (TEM). The magnetic susceptibility curve indicates that the β-Co2P nanorods show canted antiferromagnetic state, different from the paramagnetic state of orthorhombic low temperature phase β-Co2P.

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Reconstruction and appraisal of Akunu–Akoko area iron ore deposits using geological and magnetic approaches

Abstract

Geological mapping and magnetic methods were applied for the exploration of iron ore deposits in the Akunu–Akoko area of Southwestern Nigeria for the purpose of evaluating their geological characteristics and resource potentials. A proton magnetometer measures the vertical, horizontal and total magnetic intensities in gammas. The subsurface geology was interpreted qualitatively and quantitatively. The downward continuations and second vertical derivatives, the small-sized mineralised bodies and shallow features in the study area were mapped. The faults are trending in the following directions: NE–SW, NW–SE, N–S and E–W groups, while the iron ore mineralisation is structurally controlled by two major groups of fault trends, namely, the NE–SW and NW–SE; the N–S and E–W groups are mere occurrences that do not contribute to the structural control of the iron ore mineralisation in Akunu.

The upward continuation has a linear feature similar to the principal orientation of the regional faults, while Locations 2 and 3 have relatively high magnetic susceptibility zones; suspected to be iron ore deposits. The depths to the magnetic sources ranged from 25 m to about 250 m.

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Synthesis, sintering, specific heat and magnetism of Eu3S4 by low-temperature CS2-gas sulfurization of Eu2O3 nanospheres

Abstract

Single-phase Eu3S4 was obtained via CS2 gas sulfurization of Eu2O3 nanospheres at 773 K for longer than 0.5 h. The primary particle size of Eu3S4 became larger than that of Eu2O3 during the sulfurization process. Pure synthetic Eu3S4 powders were unstable and transformed to EuS at 873 K under vacuum. Eu3S4 compacts were sintered in temperature range of 773 K to 1173 K and they transformed to EuS at 1473 K during spark plasma sintering. Specific heat of sintered Eu3S4 did not show an anomalous behavior in the range of 2 K to 50 K. The magnetic susceptibility of polycrystalline Eu3S4 followed a Curie-Weiss law from 2 K to 300 K. Magnetization of polycrystalline Eu3S4 was larger than that of single crystal Eu3S4 when the magnetic field was less than 3.5 kOe.

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Geophysical investigation of banded iron ore mineralization at Ero, North – Central Nigeria

Abstract

The banded iron ore mineralization at Ero was investigated using aeromagnetic, resistivity and induced polarization (IP) methods with the aim of characterizing the deposit. Analysis of the aeromagnetic data involved the application of reduced-to-equator transformation, derivative filters, analytic signal and source parameter imaging techniques. Computer modelling of some of the identified anomalies was undertaken. The electrical resistivity and IP methods helped in discriminating between the iron ore and the host rock. The results showed that the banded iron formations (BIFs) were characterized by spherical analytic signal anomalies ranging from 0.035 nT/m to 0.06 nT/m within the granite gneiss and magnetic susceptibility of 0.007-0.014 SI. The iron ore had low chargeability (0.1-5.0 msec) and resistivity (1.5 × 102 to 2.5 × 103 Ωm). Structural features trending in the NE-SW, E-W, and NW-SE were identified, suggesting that the area had undergone many episodes of tectonic events. Depth to the BIF varied from the surface up to about 200 m. The chargeability response of the iron bodies suggested an average grade of 20%-40%, making the prospect for economic exploitation attractive.

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Study of magnetic inhomogeneity in β-Cu3Fe4V6O24

Abstract

The temperature dependence of dc magnetization and electron paramagnetic resonance (EPR) spectra of the β-Cu3Fe4V6O24 multicomponent vanadate were investigated. Dc magnetic measurements showed the presence of strong antiferromagnetic interactions (Curie-Weiss temperature, Θ ∼ 80 K) at high temperatures, while zero-field-cooled (ZFC) magnetization revealed a cusp-like maximum in low fields at Tf1 = 4.4 K, which coincides with the splitting of the ZFC and FC curves. Another maximum was registered at Tf2 = 3.0 K. These two temperatures (Tf1 and Tf2) could be regarded as freezing temperatures in the spin glass state of two magnetic sublattices of Fe1 and Fe2 ions. The EPR spectrum of β-Cu3Fe4V6O24 is dominated by a nearly symmetrical, very intense and broad resonance line centered at g eff ∼ 2.0 that could be attributed to iron ions. Below 10 K, an additional EPR spectrum with g 1 = 2.018(1) and g 2 = 2.175(1) appears, as well as a very weak line at geff = 1.99(1). The former spectrum is probably is due to divalent copper ions, and the latter line due to vanadium V4+ complexes. The temperature dependence of EPR parameters (g-factor, linewidth, integrated intensity) was determined in the range of 3–300 K. Two low-temperature maxima in the temperature dependence of the integrated intensity (at 40 and 6 K) were fitted with a function suitable for pairs of exchange-coupled Fe3+ ions. A comparison of dc magnetic susceptibility and EPR integrated intensity indicates the presence of spin clusters, which play an important role in determining the low-temperature magnetic response of β-Cu3Fe4V6O24.

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