Diamagnetic Properties Research Articles

Diamagnetic Behavior in Nanoparticle Hematite?

A paper by Mi et al. [1] suggested that certain nano-sized hematite (α-Fe2O3) particles had diamagnetic properties at room temperature. Since diamagnetic behavior is not a property normally attributed to hematite particles (hematite is generally regarded as a canted antiferromagnetic material at room temperature) we decided to test the validity of the suggestions in [1] by performing magnetic susceptibility and magnetic hysteresis measurements on a series of hematite nanoparticles with average sizes of 8 nm, 30 nm and 40 nm in diameter. We initially considered two possible explanations for the apparent diamagnetic behavior of the nanoparticles in [1]: either 1) the hematite nanoparticles themselves exhibited this unusual diamagnetic behavior, or 2) the diamagnetic response was simply the signal created by a diamagnetic dispersant that was overriding a weak positive magnetic susceptibility signal of the hematite nanoparticles. Our experiments strongly suggested the latter explanation that the apparent “diamagnetic” behavior seen in [1] was caused by a diamagnetic dispersant dominating the magnetic properties of the dispersed hematite nanoparticles.

Room temperature ferromagnetism in Cr doped SrSnO3 perovskite system

Polycrystalline SrSnO3 compounds doped with 1, 3 and 5% of Cr was synthesized by simple chemical precipitation method and the effect of doping on structural, optical and magnetic properties was investigated. Powder X-ray diffraction analysis reveals the orthorhombic structure of pure and Cr doped SrSnO3 compounds. The appearance of metal oxide vibrations were investigated by Fourier transform infra red spectroscopy analysis. Presence of active Raman modes, Sr–O and Sn–O band vibrations were examined by Raman spectral analysis. The high degree of agglomeration in pure SrSnO3 sample and formation of rod like shape of particulate system in all the Cr doped samples was identified by Electron microscopy techniques. X-ray photoelectron spectroscopy analysis discloses the oxidation states of elements and presence of oxygen vacancy in the compounds. The intriguing violet–blue emission behavior of pure and Cr doped compounds due to interaction between O 2p state and Sn 5s energy levels was observed by photoluminescence spectral studies. The magnetization studies exhibit the diamagnetic property of pure SrSnO3 compound and doping of Cr3+ in Sr–Sn–O lattice drives the carrier induced exchange interactions which results ferromagnetic phase transition in all the Cr doped compounds. From the present investigation, tunability of dia to ferromagnetism with respect to the dopant concentration (Cr3+) in SrSnO3 system at room temperature leads the material for fabrication of magneto-optical and electronic devices.

In Situ 3D Label-Free Contactless Bioprinting of Cells through Diamagnetophoresis.

Using whole blood, we demonstrate the first realization of a novel macroscale, contactless, label-free method to print in situ three-dimensional (3D) cell assemblies of different morphologies and sizes. This novel bioprinting method does not use nozzles that can contaminate the cell suspension, or to which cells can adhere. Instead, we utilize the intrinsic diamagnetic properties of whole blood cells to magnetically manipulate them in situ in a nontoxic paramagnetic medium, creating (a) rectangular bar, (b) three-pointed star, and (c) spheroids of varying sizes. We envision the technique to be transferable to other cell lines, with potential applications in tissue engineering and drug screening.

DIAMAGNETISM IN THE CYLINDRICAL QUANTUM DOT WITH PARABOLIC CONFINEMENT POTENTIAL

Diamagnetic properties of the electron gas in a cylindrical quantum dot with parabolic confinement potential have been investigated. The analytical expressions have been obtained for mean energy, mean magnetization and mean magnetic susceptibility of the electron gas. The diamagnetic character of such system has been shown.

Magnetization and diamagnetism of a longitudinal autosoliton in p-InSb in an external longitudinal magnetic field

It has been experimentally shown that a longitudinal thermal-diffusion autosoliton, which is generated in a nonequilibrium electron–hole plasma in p-InSb, in an external longitudinal magnetic field acquires diamagnetic properties. The results of the calculation and numerical estimates of the diamagnetism have been presented.

Magnetic field assisted μ-solid phase extraction of anti-inflammatory and loop diuretic drugs by modified polybutylene terephthalate nanofibers

A magnetic nanocomposite consisting of nanoparticles–polybutylene terephthalate (MNPs–PBT) was electrospun and used as an extracting medium for an on-line μ-solid phase extraction (μ–SPE)–high performance liquid chromatography (HPLC) set–up with an ultraviolet (UV) detection system. Due to the magnetic property of the prepared nanofibers, the whole extraction procedure was implemented under an external magnetic field to enhance the extraction efficiencies. The developed method along with the synthesized nanocomposite were found to be appropriate for the determination of trace levels of selected drugs including furosemide, naproxen, diclofenac and clobetasol propionate in the urine sample. The prepared MNPs-PBT electrospun nanocomposite was characterized using the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Fourier transform infrared (FT–IR) spectroscopy. The prepared magnetic fibers showed high porosity, which was another driving force for the extraction efficiency enhancement. Major parameters affecting the extraction efficiency of the selected drugs were optimized. The limits of detections (LOD) of the studied drugs were in the range of 0.4–1.6 μg L−1 and the limits of quantification (LOQ) were 1–4 μg L−1 under the optimized conditions. Relative standard deviation (RSD%) for three replicates at three concentration levels of 6, 100 and 400 μg L−1 were 5.9–8.0% while acceptable linear range with two orders of magnitude was obtained (R2 = 0.99). The method was validated by the determination of the selected drugs in urine samples and the results indicated that this method has sufficient potential for enrichment and determination of the desired drugs in the urine sample. The relative recovery values were found to be in the range of 78–91%. Implementing the developed on–line μ–SPE method under the external magnetic field induction, led to higher extraction efficiencies for the selected drugs with various diamagnetic properties.

Improving magnetic properties of MgB2 bulk superconductors by synthetic engine oil treatment

The present study focuses on the effects of standby time of the MgB2 samples immersed in synthetic engine oil on the critical current density ( Jc(H)), magnetic field dependence of the pinning force density fp(b) and Tc performances of MgB2 bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB2 pellet samples were immersed at different standby time of 30min, 120min, 300min and 1440min in synthetic engine oil after the first heating process. Finally, MgB2 samples immersed in synthetic engine oil were sintered at 1000°C and kept for 15min in Ar atmosphere. The critical current density of all of MgB2 samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB2 sample because of the number of the pinning centers. The MgB2 sample immersed at 300min standby time in synthetic engine oil has the best performance compared to other samples. The Jc value for the pure sample is 2.0×103A/cm2, whereas for the MgB2 sample immersed at 300min standby time in engine oil the Jc is enhanced to 4.8×103A/cm2 at 5K and 3T. The superconducting transition temperature (Tc) did not change with the increasing standby time of the samples in synthetic engine oil at all. The best diamagnetic property was obtained from the sample which kept in synthetic engine oil for 300min. Synthetic engine oil treatment results in remarkable improvement of the critical current density and pinning force performances of MgB2 superconductors. It was found that all MgB2 samples have a different pinning property at different measuring temperatures. Using synthetic engine oil as a product which is cheap and a rich carbon source in MgB2 bulk superconductors makes MgB2 samples immersed in synthetic engine oil a good candidate for industrial applications.

Diamagnetic susceptibility of the electron gas in the cylindrical nanolayer

Diamagnetic properties of the electron gas in cylindrical nanolayer have been investigated. The dependence of mean energy, mean magnetization and mean magnetic susceptibility on the values of magnetic field is obtained. Comparison of these dependencies with the case, when the electron gas is localized in the cylindrical quantum dot, is carried out. In a nanolayer, the character of an effect of size quantization on the magnetic properties of the electron gas has been revealed.

Origin of exotic ferromagnetic behavior in exfoliated layered transition metal dichalcogenides MoS2 and WS2.

Bulk layered transition metal dichalcogenides (TMDs) show diamagnetic properties. When exfoliated, the materials' band gap increases and changes from an indirect band gap to a direct one. During the exfoliation, the TMDs may undergo a phase transition from 2H to 1T polymorph, which is likely electronically driven and accompanied by a metal-insulator transition. A significantly higher efficiency of the exfoliation was observed using sodium naphthalenide compared to butyllithium. Moreover we demonstrate that the exfoliation has a dramatic influence on the magnetic properties of two TMDs, MoS2 and WS2. These materials become partly ferromagnetic upon exfoliation, which is a highly unexpected behavior. Exotic ferromagnetism is generally observed on samples with a high degree of exfoliation, which indicates the association of this effect with defects formed on the edges of dichalcogenide sheets. Such an exotic ferromagnetic behavior, if properly understood and brought under material engineering control, shall open the door to new applications of these materials.

Strong Static Magnetic Fields Increase the Gel Signal in Partially Hydrated DPPC/DMPC Membranes.

It was recently reported that static magnetic fields increase lipid order in the hydrophobic membrane core of dehydrated native plant plasma membranes [Poinapen, Soft Matter 9:6804-6813, 2013]. As plasma membranes are multicomponent, highly complex structures, in order to elucidate the origin of this effect, we prepared model membranes consisting of a lipid species with low and high melting temperature. By controlling the temperature, bilayers coexisting of small gel and fluid domains were prepared as a basic model for the plasma membrane core. We studied molecular order in mixed lipid membranes made of dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) using neutron diffraction in the presence of strong static magnetic fields up to 3.5 T. The contribution of the hydrophobic membrane core was highlighted through deuterium labeling the lipid acyl chains. There was no observable effect on lipid organization in fluid or gel domains at high hydration of the membranes. However, lipid order was found to be enhanced at a reduced relative humidity of 43%: a magnetic field of 3.5 T led to an increase of the gel signal in the diffraction patterns of 5%. While all biological materials have weak diamagnetic properties, the corresponding energy is too small to compete against thermal disorder or viscous effects in the case of lipid molecules. We tentatively propose that the interaction between the fatty acid chains’ electric moment and the external magnetic field is driving the lipid tails in the hydrophobic membrane core into a better ordered state.

Structural, optical and magnetic properties of Cr doped In2O3 powders and thin films

The (In1−xCrx)2O3 powders as well as thin films of x = 0.03, 0.05 and 0.07 were synthesized using a solid state reaction and an electron beam evaporation technique (on glass substrate), respectively. The influence of Cr doping concentration on structural, optical and magnetic properties of the In2O3 samples was systematically studied. The X-ray diffraction results confirmed that all the Cr doped In2O3 samples exist cubic structure of In2O3 without any secondary phases presence. The chemical composition analyses showed that all the Cr doped In2O3 compounds were nearly stoichiometric. The X-ray photoelectron spectroscopy analysis of the Cr doped In2O3 thin films showed an increase of oxygen vacancies with Cr concentration and the existence of Cr as Cr3+ state in the host In2O3 lattice. A small blue shift in the optical band gap was observed in the powder compounds, when the dopant concentration increased from x = 0.03 to x = 0.07. In thin films, the band gap found to increase from 3.63 to 3.74 eV, with an increase of Cr concentration. The magnetic measurements show that the undoped In2O3 bulk powder sample has the diamagnetic property at room temperature. And a trace of paramagnetism was observed in Cr doped In2O3 powders. However (In1−xCrx)2O3 thin films (x = 0.00, 0.03, 0.05 and 0.07) samples shows soft ferromagnetism. The observed ferromagnetism in thin films are attributed to oxygen vacancies created during film prepared in vacuum conditions. The ferromagnetic exchange interactions are established between metal cations via free electrons trapped in oxygen vacancies (F-centers).

Measurements of the complex permittivity of highly concentrated aqueous NaCl solutions and ferrofluid employing microwave cylindrical cavities

Few resonance cavities operating on different modes have been used for the accurate multi-frequency determination of the complex permittivity of highly concentrated aqueous NaCl solutions at a frequency range of 2.5 GHz to 24 GHz. It has been shown that the use of the perturbation method would lead to significant measurement uncertainties especially for lossy samples and should be avoided especially for TE0n1 mode cavities. At frequencies that are smaller than 15 GHz the imaginary part of the permittivity of NaCl solutions increases while at frequencies larger than 15 GHz it decreases, with the increasing conductivity of the electrolyte. In the last case the total dielectric losses for the saturated electrolyte are noticeably smaller than for pure water. The complex permittivity and complex permeability of ferrofluid, liquid that exhibits diamagnetic properties at microwave frequencies, were measured by employing two cylindrical cavities operating on complementary modes.

Ferromagnetism of Single-Crystalline Cu2O Induced through Poly(N-vinyl-2-pyrrolidone) Interaction Triggering d-Orbital Alteration

Ferromagnetic-like properties of cuprous oxide (Cu2O) are induced through its interaction with chemisorbed surfactant poly(N-vinyl-2-pyrrolidone) (PVP), which alters the intrinsic d10 configuration of Cu ions. Structural and magnetism-related properties of intact Cu2O crystals (i-Cu2O) and those capped with PVP (c-Cu2O) were examined using various analytical instruments. SEM, TEM (corresponding selected area electron diffraction (SAED)), and XRD of i-Cu2O and c-Cu2O showed cubic and hexagonal shapes of single crystallinity with facets of {200} and {111}, respectively, resulting from the differential growth rates of the original identical crystals along the facets over time. Bulk magnetic susceptibility (χ) of i-Cu2O and c-Cu2O at room temperature in field-dependent magnetization and the difference in their magnetic moment in temperature-dependent magnetization showed diamagnetic and ferromagnetic properties, respectively. The difference in the fluorescence mode of X-ray absorption near edge structure (XANES) spectra between i-Cu2O and c-Cu2O, showing no quadruple pre-edge peak for the transition 1s → 3d in Cu(II) ions with d9 electronic configuration, indicates an orbital alteration on the surface of c-Cu2O caused by an interaction with PVP. Two peaks for c-Cu2O at higher binding energies in O 1s X-ray photoelectron spectroscopy may be indicative of the ligand-to-metal charge transfer (LMCT) from O atoms of PVP to Cu ions of Cu2O, generating a chemical interaction through coordination bonding. Large hyperfine splitting constants in electron paramagnetic resonance (EPR) spectra of c-Cu2O support this interpretation, with septet hyperfine splitting suggestive of Cu–Cu interactions on the surface of c-Cu2O via the interaction with O atoms of PVP. These results demonstrate that PVP capping of Cu2O crystal (c-Cu2O) induces ferromagnetism of Cu(I) ions through coordination with O atoms of chemically adsorbed PVP. This may induce LMCT and Cu–Cu interactions that lead to changes in electronic configurations, deriving the ferromagnetic moments of c-Cu2O.

Impact of Trapped Helium Gas Bubble in Liquid Helium on the Cooling in High Magnetic Field

Liquid helium is used as the coolant for high field superconducting magnets or samples tested in the high magnetic field at the National High Magnetic Field Laboratory. When the magnetic field is ramping up, the boil-off helium gas generated by heat losses in the coil and from external environment of the cryostat can be trapped in the liquid helium bath in a region where Bz · dBz/dz is less than -2100 T 2 due to the weakly diamagnetic property of helium. It results to the surfaces of the magnet or samples being covered partially or even fully with the accumulated helium gas instead of liquid helium. The very low thermal conductivity of helium gas may cause an inefficient cooling for the magnets or samples. In the beginning stage of YBCO coils development, the trapped gas bubble caused a temperature increase in the region of trapped gas bubble and prevented the test coils ramped up to a higher current. This raised an issue for the cooling of the 32-T magnet, which is to be cooled in a liquid helium bath, because the trapped gas bubble may cause inefficient cooling of the magnet in this gas bubble region. Relevant tests were performed, and the trapped gas bubble was observed in recent tests of the 32-T magnet prototype coils. The impact of the gas bubble on the cooling of the 32-T YBCO prototype coils was tested, and the test results are presented.

Ferroic properties of Fe-doped and Cu-doped K0.45Na0.49Li0.06NbO3 ceramics

Ferroelectric and magnetic properties of Fe-doped K0.45Na0.49Li0.06NbO3 (KNLN) and Cu-doped KNLN ceramics were investigated. Comparing with pure KNLN ceramic, Fe-doped KNLN shows ferromagnetic and ferroelectric properties simultaneously while Cu-doped KNLN shows stronger diamagnetic and ferroelectric properties. The magnetic property in KNLN matrix are believed to be induced by point defects. The ferromagnetism of Fe-doped KNLN can be explained by the F-center exchange mechanism, while the antiferroelectric-like loop and diamagnetism of Cu-doped KNLN was explained by the special defect structure and Cu1+ ion at A site.

Flux jump behaviors and mechanism of FeTi doped MgB2 at 5 K

This study examined the flux jump behaviors of Fe-doped MgB2 according to content of FeTi particles at 5K, at which flux jump has been shown to be more frequent. The samples were synthesized in a stainless steel tube with Mg, B and FeTi particles. The motives of flux jump in MgB2 superconductors are over-moving fluxes around the defects and the low heat capacity of MgB2. MgB2 was doped with FeTi particles to overcome these vulnerable points of MgB2. The flux jump of MgB2 decreased with increasing content of doped FeTi particles. On the other hand, excessive doping of FeTi resulted in a decrease of diamagnetic properties and the flux pinning effects together. It is concluded that FeTi particles in MgB2 do not block the flux jump itself, but the propagation of flux jump of MgB2.

Pioneering the application of diamagnetic materials for spacecraft attitude control

Developed by a student team at the University of Victoria, the ECOSat2 cube satellite is a demonstration platform for communications and attitude control technologies useful in small satellites. Its scientific payload is an experimental attitude control actuator that uses a diamagnetic material called pyrolytic graphite. We seek to demonstrate that this diamagnetic effect can be used to control the attitude of small satellites in Earth orbit, and thereby inspire research into developing materials with stronger diamagnetic properties and further their use in spacecraft control.

Influences of Ni Doping on the Morphology, Optical and Magnetic Properties of ZnO Nanostructures Synthesized by Solvothermal Process.

Pure and Ni-doped ZnO nanostructures have been synthesized by a solvothermal process. The structure, morphology and properties of as-synthesized samples have been investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), selected-area electron diffraction (SAED), UV-vis spectrometer as well as by vibrating sample magnetometer (VSM). XRD and EDS studies indicated that the as-prepared products were well-crystallized wurtzite hexagonal structure. The SEM and TEM images show that the individual Zn0.96Ni0.04O nanostructure is composed of several nanorods with average diameter of 200 nm and lengths of 500 nm. The structure and morphology analyses show that Ni doping can influence the nanostructures morphology, but cannot change the crystal structures of ZnO samples. The UV-vis spectra showed that Ni dopant can result in an appreciable blue-shift for the absorption edge of the Ni-doped ZnO samples. The band gap energy of the Zn0.96Ni0.04O nanostructure was about 3.23 eV. By magnetic measurements, it was observed that the pure ZnO nanostructure exhibits diamagnetic property while the sample of 4% Ni shows an obvious ferromagnetic behavior at room temperature due to the formation of solid solution Zn0.96Ni0.04O, sp-d and d-d carrier exchange interactions, and the presence of abundant defects and oxygen vacancies.

Strong magnetic field-assisted growth of carbon nanofibers and its microstructural transformation mechanism.

It is well-known that electric and magnetic fields can control the growth direction, morphology and microstructure of one-dimensional carbon nanomaterials (1-DCNMs), which plays a key role for its potential applications in micro-nano-electrics and devices. In this paper, we introduce a novel process for controlling growth of carbon nanofibers (CNFs) with assistance of a strong magnetic field (up to 0.5 T in the center) in a chemical vapor deposition (CVD) system. The results reveal that: 1) The CNFs get bundled when grown in the presence of a strong magnetic field and slightly get aligned parallel to the direction of the magnetic field; 2) The CNFs diameter become narrowed and homogenized with increase of the magnetic field; 3) With the increase of the magnetic field, the microstructure of CNFs is gradually changed, i.e., the strong magnetic field makes the disordered “solid-cored” CNFs transform into a kind of bamboo-liked carbon nanotubes; 4) We propose a mechanism that the reason for these variations and transformation is due to diamagnetic property of carbon atoms, so that it has direction selectivity in the precipitation process.

Comparative Study of the Hydrogenation of Cu and TM (Mn,Fe,Ni)-Codoped ZnO Nanocomposite DMS

Solid solution (SS) composite nanocrystallite powders of zinc oxide (ZnO) codoped with Cu and transition metal (TM) ions (where TM stands for Mn, Fe, Ni) were synthesised by thermal co-decomposition of a mixture of Zn, Cu, and TM acetylacetonates. The molar % content of Cu (1 %) and TM (2 %) were fixed in all the prepared SSs. The synthesised powders were post-annealed in hydrogen atmosphere at 500 ◦ C for 1 h. The X-ray diffraction (XRD) study confirmed the formation of single phase of nanocrystalline SS based on ZnO structure. The optical study shows red shifts in the bandgaps of SSs. The magnetic study at room temperature (RT) revealed that all the prepared SSs based on ZnO powders have gained overlapped paramagnetic (PM) with ferromagnetic (FM) properties defeating the diamagnetic (DM) properties of ZnO. The gained partial RT-FM properties have different behaviours and energy depending on the type of TM dopant. Furthermore, it was found that the created RT-FM is clearly enhanced by H2 post-annealing at 500 ◦ C for 1 h. Therefore, with hydrogenation, the saturation magnetisation for Ni dopant increased by ∼ 141 % and for Fe dopant by ∼ d almost only RT-FM that was enhanced by hydrogenation, which was explained by the high carrier density in magnetic exchange interactions (MEI) medium.