جستجوی مقالات مرتبط با کلیدواژه « magnetic susceptibility » در نشریات گروه « فیزیک »

In this study, we investigate the trajectory of magnetic nanoparticle flowing through a microvessel in the presence of cylindrical magnet. By using the equation of motion of particle in the presence of magnetic and fluidic forces, the motion trajectory of magnetic particle in the microvessel is calculated. Our numerical results show that the probability of trapping magnetic particles in the straight microvessel is a function of the intensity of the magnetic field, particle radius, particle magnetization, and diameter of vessel. In this study, we investigate the effect of particle radius, magnet magnetization, particle saturation magnetization and vessel radius on the trajectory of magnetic nanoparticle flowing through the straight vessel. The results show that with increasing particle radius, magnet magnetization, particle saturation magnetization and also with decreasing vessel radius, the probability of trapping a floating particle in the channel increases

Because of declining high-grade ore deposits and increasing demands for metal resources, exploration of low-grade metal deposits, such as porphyries, have become feasible. Besides, humankind has spent most of the shallow metal ore deposits, and new prospecting projects focus on deeper deposits. Therefore, geophysical methods have gained more attention due to their ability to determine buried ore bodies' physical properties. Hence, most countries, including Iran, make significant investments in the geophysical exploration of deep porphyry deposits. According to widely accepted Lowell and Guilbert's model for porphyry copper deposits, the ore-bearing zones mainly concentrate at the edge of the potassic alteration zone. Pyrite, a highly conductive and chargeable metallic mineral, is a significant attribute in the potassic alteration. The model also states that the high susceptible magnetite-bearing rocks mainly occur at the bottom of the pyrite shell and the ore body. Due to the occurrence and presence of susceptible and conductive metallic minerals such as magnetite and pyrite in the potassic zone near to the ore body in the copper and gold porphyry deposits, the use of magnetometry, resistivity, and inducing polarization methods give reliable information about the location, depth, and shape of the deposits. For instance, in this research, we focus on the magnetic and IP/Res data in the southern Dalli porphyry deposit, with promising Cu-Au indices, which is located at Euromieh-Dokhtar ore-bearing zone Markazi Province. First, we applied standard processing techniques to remove the aliasing and regional effect in the magnetic data. Then, using the analytic signal technique, we showed the concentration of the magnetic sources over the study area. We also applied the power spectrum and Euler deconvolution techniques to the magnetic data and estimated the magnetic sources' depths. The estimated depth from the power spectrum is between the estimated depth from Euler deconvolution for possible sources with step and pillar shapes. Next, we used the average estimated depth from each of the depth estimation techniques in a three-dimensional magnetic data inversion as the depth of the sources in depth weighting. Also, we studied the inversion results via combining the cross-section of the magnetic susceptibility model along the boreholes and the lithology and geochemical information from core samples analysis. The results indicate that the higher grades for gold and copper occur at the edge of the magnetic sources and possible magnetite mineralization zones. The inversion results using the depth weighting with the depth extracted from the power spectrum show the best correlation and spatial relation with the geochemical data. Besides the magnetic data inversion, applying Oldenburg and Li algorithms for two-dimensional inverse modeling, we extracted the underground bodies' resistivity and chargeability model along with a IP/Res profile in the study area. The resulting chargeability models show a significant relationship with the presence of gold and copper mineralization. We also compared the resulting two-dimensional resistivity and changeability models with their corresponding magnetic susceptibility at the cross-sections along with the IP/Res. The comparison shows that the possible mineralization zones coincide with larger magnetic susceptibility values, high chargeability and low resistivity. The results show good accordance with Lowell and Guilbert's model. Also, highly susceptible rock in the shallower depth indicates that the erosion process has destroyed most possible orebody.

In this study, the density of states, heat capacity, and magnetic susceptibility of carbon nanodiscs and nanowires with different diameters are calculated via the tight-binding approximation and the Green’s function approach. The results indicate that by increasing the diameter, the nanodiscs move from a semi-conductive and tend toward a semi-metal which is in agreement with other theoretical works. Also, increasing the diameter of the nanowires causes them to exhibit a metallic behavior. It is observed that increasing the diameter of these nanostructures increases the number of the Van Hove singularities in the density of states diagrams. A Schottky anomaly peak is seen in the heat capacity curves of these two nanostructures, which for the nanodisc/nanowire with the largest diameter, has a lower height. Due to the presence of the Van Hove singularities in the density of states diagram, a crossover is seen in the magnetic susceptibility curves, which splits these diagrams into two high temperature and low temperature regions. It is also concluded that at low temperatures, increase in the diameter of the nanodiscs and nanowires increases the magnetic susceptibility. These maximum values are also observed in the heat capacity and magnetic susceptibility curves of other graphene and graphene-like nanostructures.

The high-Tc Y1-xNixBa2Cu3O7-δ samples doped by Ni for Y atom, with x=0, 0.002, 0.004, 0.006 and 0.01 were synthesized by the standard solid-state reaction method. The XRD diffraction of samples showed no impurity phase in all samples. Magnetic susceptibility of the samples under two different magnetic fields of 0.8 and 400 A/m was measured. The results showed that by increasing nickel element to an optimum value, the intragranular connection and flux pinning were improved.

In this research single phaseLa0.7(Sr 1-xBax)0.3MnO3(x =0, 0.1 , 0.2 , 0.3) nanomanganite with crystalline size of 18-28 nm have been prepared by sol gel method. The structural properties have been studied using X-ray diffraction spectra with its Rietveld analysis and scaning electron microscope images. The magnetic and elctrical properties have been investigated by measuring the ac magnetic susceptibility and resistivity in the presence of magnetic fields in the range of 0-20 kOe. The obtained results from ac magnetic susceptibility show that the Curie temperture of the samples are above room temperture. The results of resistivity show that the metal-insulator phase transition temperture of La0.7 Sr0.3 MnO3 and La0.7 (Sr0.3 Ba0.2) MnO3 compounds are below room temperture. The resistivity of the samples strongly decreases and their magnetoresistance almost linearly increases by incrasing the applied magnetic field at different tempertures. The value of magnetoresistance for La0.7 (Sr0.3 Ba0.2) MnO3 Ecompound is 10 % and 14 % at 275 K and 200 K, and for La0.7 Sr0.3 MnO3 Ecompound is 13 % and 27 % at 275 K and 100 K, respectively which are suitable for magnetic field sensing applications. The magneto-transport properties of La0.7 (Sr1-x Bax) MnO3 nanomanganite are described in terms of spin dependent scattering of charge carriers from grain boundaries and their spin dependent tunneling between grains.

Carbon nanotubes (CNT) were synthesized by CVD method based on Ni (NO3) 2. 6H2O and Co (NO3) 2. 6H2O solution with two different ratios [Ni/Co = (1/ 0. 5)، (1/ 0. 0)]. We obtained the magnetic properties of the samples، such as coercivity field، saturate magnetization، retentivity magnetization and magnetic susceptibility by using of the magnetic hysteresis loops. It was found that carbon nano tubes were synthesized by using combination of Ni (NO3) 2. 6H2O and Co (NO3) 2. 6H2O catalysts، have much higher coercivity field، but less retentivity magnetization and saturation magnetization compared with the nanotubes were synthesized by using of the only Ni (NO3) 2. 6H2O catalyst