Papers by Keyword: Magnetic Susceptibility

Abstract: The suppression of superconductivity (T_c) in electron-doped superconducting materials Eu_1.81Ce_0.19Cu_1-yZn_yO_4+α-δ (ECCZO) heavily overdoped regimes by nonmagnetic impurity Zn with concentration of y = 0, 0.01, 0.02, and 0.03 has been successfully investigated by using XRD and SQUID measurements. All samples were synthesized using the solid-state reaction method. The crystal structure obtained from XRD measurements has a tetragonal T° structure, which matches the crystal structure of electron-doped superconductors in general. The addition of Zn impurity shows no change in the crystal structure, but there is a decrease in the α-lattice and an increase in the c-lattice, unit cell volume, and Cu-O bond length. This causes the distance between the charge reservoir and the conduction layer to increase and affects the disappearance of T_c. Magnetic susceptibility measurements using SQUID were carried out under FC (Field Cooling) conditions with temperatures between 2 - 30 K with a field of 5 Oe. The sample with y = 0 has diamagnetic properties with a superconductivity value (T_c) of about 11 K. The addition of Zn impurities succeeded in suppressing superconductivity as indicated by the disappearance of T_c, so that the sample is in the ground state. The Curie constant and the effective magnetic moment decrease with increasing Zn concentration. This is probably due to the decrease in Cu²⁺ when the non-magnetic Zn²⁺ atoms were added, therefore the overall value of the µ_eff decreases when Zn²⁺ substitutes some Cu²⁺. This result is different from that described by Abrikosov-Gor’kov theory in the hole-doped high-T_c cuprates.

Abstract: Differences in particle size can affect the magnetic properties of superconductors. At the nanoscale, superconductors have different magnetic properties than those at the micro or submicron size. The difference in particle size in superconducting materials can be obtained by giving the sintering temperature difference. In this work, we focus only on the magnetic properties in Eu_1.85Ce_0.15CuO_4+α-δ (ECCO) in the optimal-doped regime prepared by the sol-gel method with various sintering temperatures 700 °C, 800 °C and 900 ° C sizes with an annealing temperature 800 °C to obtain different particle. The lattice parameters and crystallite size were obtained using XRD. Based on the XRD results, the higher the sintering temperature variation, the larger the crystallite size produced with lattice distortion and expansion with a decrease in particle size. The magnetic properties of these materials have been investigated using a superconducting quantum interference device (SQUID) at temperatures between 2 K and 30 K with the applied field at 5 Oe. Based on the SQUID measurement, the magnetic properties of samples sintering at 700 °C and 800 °C were found to be ferromagnetic-like behaviour, while sintering at 900 °C was found to be paramagnetic with no trace of the superconductivity phase. The differences response of magnetic properties can be associated with the effect of the differences size of the crystallites in each material, that can relate to uncompensated spins produced by the surface effect.

Abstract: There is a lack of information on the magnetic properties of particles of such materials as powder magnetic (modified by inclusions of magnetite and maghemite) carbon sorbents intended for water purification from various kinds of impurities and, what is especially important, allowing to perform the prompt isolation of the spent sorbent – by magnetic separation. The data on the magnetic susceptibility χ of the particles of these sorbents, found by the developed experimental calculation method based on the concept of the corresponding magnetometry of a moderately rarefied dispersed sample with a dispersed phase of the particles under study, are presented. Experimental dependences of the magnetic susceptibility of <χ>of a dispersed sample on the volume fraction γ of controlled particles in it have been obtained - for different values ​​of the magnetic field strength H in the range from 22 to 61 kA/m, i.e. in the postextremal region for the susceptibility. In addition to the necessary assessment of their linear, located at γ ≤ 0.15-0.2, sections, this also made it possible to find and phenomenologically describe the field dependences of the generalized data of the reduced susceptibility of <χ>/γ, i.e. data χ: in the form of an inverse power function with a power of 0.7 ... 0.8 at H.

Abstract: Graphene oxide (GO) is 2D material made of honey comb carbon structure as backbone and decorated by oxygen functional groups in both sides. These functional groups have role to the GO properties, such as magnetic susceptibility, band gap, conductivity. There are several processes to reduce its oxygen content, such as chemical, photo and thermal reduction, resulted reduced graphene oxide (rGO). Several studies reported the magnetic properties of GO and rGO correlating with the process of synthesis and reducing oxygen contents. We report the magnetic characteristic of a commercial GO 0.5 mg/ml dispersed in H₂O from Graphenia and RGO that were synthesized through thermal reduction process of GO precursor. In this process, we use oven vacuum system at 200 °C for 1 hour. All samples were prepared as GO and rGO thick films. The GO and rGO samples structure were indentified from XRD data and SQUID data for magnetic characteristics. We explored the temperature dependence of magnetic susceptibility by applying magnetic field of 500 Oe in Zero Field Cooling (ZFC) and Field Cooling (FC). The result shows different susceptibility behavior of GO and rGO samples in all wide range of temperature between 0 to 300 Kelvin. The value of magnetic susceptibility rGO is higher than that of GO and has splitting curve of ZFC and FC at low temperatures below 200 Kelvin. However, GO has the splitting curve of ZFC and FC occurred at high temperatures above 200 Kelvin.

Abstract: One of the pyrochlore systems, Nd₂Ru₂O₇, shows unique magnetic properties and can be a candidate of the electrocatalyst material for industrial applications. This system shows magnetic anomalies around 1.8 K, 21 K, and 146 K. The anomaly at 21 K is suggested to be coming from the impurity component of Nd₃RuO₇ and is still debatable. To investigate the effects of impurities on the magnetic properties of this sample, we synthesized some samples (labelled as Sample-I and II) using the solid-state reaction method with different heat treatment conditions and measured the magnetic susceptibility. We found that low sintering temperatures generated impurity phases of raw materials and Nd₃RuO₇. We also confirmed that those impurity phases were able to be reduced by optimizing heat treatment conditions. The optimum temperature for the sintering process should not be higher than 1000°C. The higher sintering temperatures yield more Nd₃RuO₇ impurity phases. Magnetic susceptibility measurements showed that samples with Nd₃RuO₇ impurity phases exhibited a peak around 21 K in the zero field-cooled condition accompanied by a broad peak around 12 K in the field-cooled condition indicating the appearance of Nd₃RuO₇.

Abstract: The partially substitution of magnetic impurity Ni for Cu in electron-doped superconducting cuprates of Eu_2-xCe_xCu_1-yNi_yO_4+a-d with x = 0.14 and y = 0, 0.01 and 0.02 has been studied in order to investigate the effect of Ni impurity on structure and the value of magnetic moments per unit volume extracted from susceptibility data in under-doped region. Magnetic-susceptibility measurements were carried out at low temperatures down to 2 K. For sample with y = 0, diamagnetic behavior is observed starting from about 9 K. The superconductivity disappeared at y ³ 0.01. The values of magnetic moment in every volume unit decreased with increasing Ni.

Abstract: Magentic separation generally required strong magnetic forces induced in ferromagnetic or strong paramagnetic particles; in order to realize the separation in diamagnetic or weak paramagnetic particles, it was necessary to attach magnetic beads or magnetic ions to induce the strong magnetic force. A method to separate mixture of weak magnetic particles by its concentration of paramagnetic ferrous ion is newly proposed, which does not require the abovementioned magnetic attachments. The efficiently of the new method is experimentally examined using a pocketsize magnetic circuit (4.5 cm x2.0 cm x 1.0 cm) and a piece of cross sectional paper (5.0 cm x1.0cm). The separation is based on a principle that velocity of a translating particle, induced by a magnetic volume force in an area of monotonically decreasing field, is uniquely determined only by its magnetic susceptibility (per unit mass) of the particle; the velocity is independent to mass of particle. By examining the spectra of the separated particles recovered on the cross sectional paper, a histogram on Fe concentration is easily obtained for the particles without the need of consuming them.

Abstract: Analysis on magnetic minerals of iron sand in Sampulungan Beach, Takalar Regency based on magnetic susceptibility value has been conducted. Iron sand was taken on 30 points and extracted using a rod magnet, then measured magnetic susceptibility using Bartington susceptibility meter MS2 with the MS2B sensor. Furthermore, types of magnetic minerals were analyzed based on the value of magnetic susceptibility. The results showed that the percentage of magnetic mineral was higher along the trajectory near residential areas. Magnetic susceptibility values ranged from 33932.62 x 10^-8 m³/kg to 71829.96 x 10^-8 m³/kg. Based on the value of magnetic susceptibility, the dominant type of magnetic mineral in Sampulungan Beach is magnetite (Fe₃O₄) of 76 wt.%. The high magnetite potential in Sampulungan Beach can be further processed to be used in the metal industry.

Abstract: Crystals of the solid solution Tm(Al_1-xMo_x)B₄ (x = 0.002 - 0.050) were grown from Tm₂O₃, metal Mo and crystalline boron powders as starting materials under an Ar atmosphere at 1773 K for 5 h. Tm(Al_1-xMo_x)B₄ crystals were obtained as a single phase in the case of Al_1-xMo_x flux (x = 0.005 and 0.010). Tm(Al_1-xMo_x)B₄ crystals at a maximum size of about 2.2 mm were obtained in the shape of a flake, and together with needle-like crystals of MoAlB and an unknown phase using Al_0.970Mo_0.030 flux. The lattice constants of Tm(Al_1-xMo_x)B₄ (x = 0.005 - 0.010) crystals were determined to be larger compared to those obtained for TmAlB₄. This is related to the fact that the ionic radius of Mo is larger than the ionic radius of Al. When the Al position in the TmAlB₄ structure was substituted with Mo having a large ionic radius, the hardness hardly changed. In contrast to TmAlB₄, no antiferromagnetic transition could be observed for Tm(Al_0.995Mo_0.005)B₄, indicating that the disorder introduced by Mo-doping disrupted the magnetic transition.

Abstract: Crystals of the quaternary compounds α-Lu(Al_1-xT_x)B₄ (T = Fe, Cr) (YCrB₄-type, orthorhombic, Pbam), obtained from the nominal composition of Lu(Al_1-xT_x)B₃, were grown by using Al flux mixed with T metal at 1773 K for 5 h under an Ar atmosphere. The maximum dimensions and morphology of the crystals obtained were about 0.7 mm × 0.5 mm for flake-type crystals of Lu(Al_1-xCr_x)B₄ and about 5.2 mm × 0.2 mm for prism crystals of Lu(Al_1-xFe_x)B₄. The lattice constants determination and chemical analyses of Lu(Al_1-xT_x)B₄ (T = Fe, Cr) compounds were carried out for Fe 0.5 - 10.0 at% and Cr 0.5 - 1.0 at%. The lattice constants and the unit lattice volume in Lu(Al_1-xT_x)B₄ crystals decreased with increase of the concentration of Fe or Cr. The values of micro-Vickers hardness of Lu(Al_1-xFe_x)B₄ (x = 0.005 - 0.030) and Lu(Al_1-xCr_x)B₄ (x = 0.005 - 0.010) samples are in the ranges of 16(2) - 20(3) GPa and 13(2) - 16(3) GPa, respectively. The hardness values showed a little increase as the solid solution of Fe or Cr was realized in Lu(Al_1-xT_x)B₄, possibly because of distortion to the crystal structure. The magnetic susceptibility of as-grown Lu(Al_0.995Fe_0.005)B₄ crystals for example, exhibited diamagnetic behavior with a small ferromagnetic component.