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Magnetic nanoparticles are of great interest due to structure and composition of materials. MNP consists of cations, e.g., Fe, Ni, Co, Cr, and their oxides, such as magnetite (Fe3O4), maghemite (γ- Fe2O3), hematite (α- Fe2O3), cobalt ferrite (Fe2CoO4), and chromium dioxide (CrO2). Magnetic nanoparticles are gaining interest due to their useful electrical and magnetic properties and applications in magnetic storage, recording media, photo catalysis, and medical diagontics as well as in solar energy applications. Magnetic nanoparticles are regarded as the most practically important and useful due to its simple synthesis and the interesting magnetic characteristics of its nano-sized objects. This review summarizes recent commercial, industrial and bio-engineering applications and brief study of the methods for the preparation of magnetic nanoparticles with a control over the size, morphology and the magnetic properties. [ABSTRACT FROM AUTHOR]

Reverse sign spectra of the Verdet constant V(ħω) in the optical active crystals Bi12SiO20 and in the doped optical active crystals Bi12SiO20:M (M = Co, Fe) are observed in the spectral region of the excitons. The spectral region, in which the sign of the doped crystals are changed, is shifted as opposed to the one of undoped crystals and the energy of the photons ħω, at which is observed an inversion of the sign of the V(ħω) of doped crystals, is less than the one of the undoped crystals. By an exchange interaction between the localized paramagnetic ions Co2+ (or Fe3+) and the charge carriers forming the excitons is explained the reverse sign spectra of the doped crystals Bi12SiO20 in the spectral region of the excitons. For undoped crystals, this effect is described by the main internal defect (Bi3+Si+h+) in Bi12SiO20. A simplified model is proposed that explains changing of the sign of V(ħω) by one exchange interaction of the ligand ion O− with a connected exciton (e− + h+) in this defect [ABSTRACT FROM AUTHOR]

11B NMR chemical shifts of structurally similar diamagnetic and paramagnetic molecules are obtained using fourcomponent relativistic DFT calculations. The calculated chemical shifts of the diamagnetic molecules are compared with those of the paramagnetic molecules to get an insight on the influence of the unpaired electron on the 11B chemical shifts. [ABSTRACT FROM AUTHOR]

The stochastic Brownian particle-kinetics in a superparamagnetic ferrofluid at room temperature is of significance in nullifying total magnetization vectors of the suspended particles. Correspondingly, the apparent magnetization response observed under static magnetic field shows no hysteresis loop, but being linear at a given finite field-difference. Owing to this superparamagnetism, we propose a differential magnetometry to analyze the static fieldinduced particle-kinetics and further to identify the effective field-strength in reorienting particle-moments toward the applied field direction. A polydispersive ferrofluid containing iron-oxide nanoparticles, in practice, is subjected to a verylow oscillatory-field, immediately after applying the static-field. For a given frequency, we confirm a decreasing ac susceptibility as dc field-strength increases, which suggests a statistically less fluctuating magnetization-vectors. Via numerical integration of ac susceptibility recorded, we furthermore estimate the nonlinear quasi-static magnetization at various measurement frequencies. The resulting nonlinearity is attributable to the contributing relaxation dynamics of the particles. More importantly, the difference between dc and ac susceptibilities is found to be field-strength and frequencydependent. Its value is further maximized at an effective field-strength, from which we identified the coexisting energybarriers. [ABSTRACT FROM AUTHOR]

Magnetic resonance-guided radiation therapy (MRgRT) benefits from performing treatment response assessments at the beginning and end of treatment and also during the treatment itself allowing for more normal tissue sparing and better tumor conformality. Gel dosimeters have been shown to demonstrate 3D dose distributions from conventional treatment units. This qualitative study assessed the value of gel dosimetry to measure volumetric dose distributions delivered by an MR-linac (MRL) while using the MR component for readout. Polymer gels in custom-designed glass cylinders of 5 cm diameter and 4 cm height were obtained from MGS Research Inc. (Madison, CT). In addition, Fricke-type dosimeters were prepared in-house with 0.05 mM xylenol orange. For this preliminary study, the dosimeters were irradiated in air, with a part of each dosimeter outside the treatment field to act as a reference. MR imaging was performed with the MRL to observe the change in paramagnetic properties pre and post irradiation using a T2 sequence for polymer gels and a T1-weighted sequence for Fricke gels. MRI during irradiation was done in the MRL using a fast sequence of TR = 5 ms and TE = 1.7 ms. Spin-spin relaxation rate (R2) maps were generated from the polymer gel images and line profiles across the penumbra were analyzed. R2 has previously been shown to be proportional to absorbed dose. When Fricke dosimeters are exposed to ionizing radiation, ferrous ions are oxidized to ferric ions. The paramagnetic spin changes, which are dependent on the concentrations of ferrous and ferric ion species, were observable on T1-weighted images due to changes in the spin-lattice relaxation rate (R1 = 1/T1). We observed a mean increase in pixel value of 53% from un-irradiated to irradiated regions of about 20 Gy. The increase in pixel value and corresponding dose was visible during irradiation using a fast MR sequence. The polymer gels also responded quickly. At 5 minutes after irradiation, the line profiles on the R2 map through the penumbra region showed the fall-off of the radiation field in both dosimeters. 20 hours after irradiation the polymerization of the gel was presumably completed. The overall signal was both higher on the R2 gray scale maps and more pronounced on the R2 color maps. The line profiles across the penumbra regions exhibited a similar trend for both field edges compared to the profiles at 5 minutes post-irradiation. Over the time frame tested, the dosimeter appears stable. These qualitative results indicate that gel dosimetry offers a promising means of measuring relative volumetric dose distributions delivered by an MR-Linac. [ABSTRACT FROM AUTHOR]

The magnetization of two electron InAs quantum dot has been studied as a function of magnetic field. The electron-electron interaction has been taken into account by using exact diagonalization method numerically. The magnetization at zero external magnetic field is zero and increases in the negative direction. There is also a paramagnetic peak where the energy levels cross from singlet state to triplet state. Finally, the magnetization falls again to even negative values and saturates. [ABSTRACT FROM AUTHOR]

The magnetic susceptibilities, of R-M and R-M-B exchange enhanced paramagnets where R = Y, La, Lu and M= Co, Ni are analysed. As a general feature, there is a T² dependence of values at T < 10 K, while for T > T* a Curie-Weiss behavior is shown. The experimental data are discussed in correlation with band structure calculations. The pressure dependence of LuCo2 magnetic susceptibility is also analysed. [ABSTRACT FROM AUTHOR]

Nanoparticles of CoFe2O4 were prepared through coprecipitation method. The particle size from Scherrer equation is 49.84 nm. The particles approach the state of superparamagnetism although the study is conducted below the temperature when the state is achieved. Some unusual unanticipated peaks have been observed in FC (field cooled) and ZFC (zero field cooled) curves and we have tried to explain them on the basis of domain wall pinning. Another feature is the large coercivity and low saturation magnetization of CoFe2O4 particles at 5K in comparison to lower coercivity and larger saturation magnetization at 300K which is attributed to anisotropy. [ABSTRACT FROM AUTHOR]

Behavior of the paramagnetic susceptibility in Si:P at low temperatures was investigated by Electron Spin Resonance in order to detect the antiferromagnetic and ferromagnetic ordering in the vicinity of the insulator-metal phase transition. The procedure was developed to operate sufficiently smooth changes of the spin density, by proton irradiated. [ABSTRACT FROM AUTHOR]

In this article, we report the systematic studies and correlations of the microstructural, magnetotransport and magnetic properties of Dy28Fe72 granular thin film, which has been prepared by dc magnetron sputtering at room temperature. The structural properties showed that the distribution of grains was uniform throughout the film and the average grain size of Fe and Dy particles was measured to be ~ 2 nm. The magnetoresistance [MR] increased from 3 to 18 % with decrease in temperature from T = 300 to 4.2 K and we have obtained a maximum of 18 % of MR at T = 4.2 K. The MR and magnetization curves have not saturated even for very high fields (H = 9 Tesla) and at all temperatures which was essentially due to the superparamagnetic (SPM) particles. SPM nature of the film was also inferred by corroborating the field dependence of magnetization and MR. [ABSTRACT FROM AUTHOR]

We communicate here a tight binding theoretical model study of the band filling effect on the charge gap in graphene-on-substrate. The Hamiltonian consists of nearest neighbor electron hopping and substrate induced gap. Besides this the Coulomb interaction is considered here within mean-field approximation in the paramagnetic limit. The electron occupancies at two sublattices are calculated by Green's function technique and are solved self consistently. Finally the charge gap i.e. Δ= U[n〈a〈-〈nb〈] is calculated and computed numerically. The results are reported. [ABSTRACT FROM AUTHOR]

We report on our measurements of local and bulk magnetic features in weakly Mn doped ZnGeP2. Utilizing muon spin rotation and relaxation measurements, we identify local ferromagnetic order and fluctuations in the local fields as sampled by an implanted muon (μ+). We also report on field induced ferromagnetism occurring above the claimed paramagnetic to ferromagnetic transition temperature (Tc = 312 K) [ABSTRACT FROM AUTHOR]

This paper reports the influence of the annealing in air and argon atmosphere on the structural and magnetic characteristics of Co-doped ZnO powders. XRD studies reveal a wurzite- type structure, while the formation of Co3O4 secondary phase was evidenced by Raman spectroscopy only for the sample annealed in air. A ferromagnetic behavior was observed for the sample annealed in air atmosphere and this behavior was explained. The sample annealed in argon atmosphere presents a paramagnetic behavior. [ABSTRACT FROM AUTHOR]

Paramagnetic 13C NMR chemical shifts of iron-bound cyanide ions located in biological environments such as heme-proteins are significantly sensitive to the environments. These chemical shifts are due to negative spin density at 13C induced by the open-shell iron center. In order to examine the environments effects on the electronic states around heme parts, ab initio calculations were performed for model systems of heme-proteins. The proximal residues in proteinparts of cytochrome c, hemoglobin, myoglobin and horseradish peroxidase were included in the model systems with the common active site (cyanide imidazole porphyrinato iron(III)) to take account of the environments effects. The calculated paramagnetic shifts of model systems reproduce the experimental trend of corresponding heme-proteins. It is found that the effects of proximal residues on the electronic states of the heme-parts are significant for these hemeproteins. In this abstract we focused on the calculations and analysis of cytochrome c. [ABSTRACT FROM AUTHOR]

The thirst to design high density magnetic storage media with improved efficiency has always been one of the basic challenges in computer industry. In this paper, present challenges of magnetic storage media and different parameters that can affect the properties of magnetic nanowires have been investigated in detail. The magnetic nanowires are the promising candidate for the future high density magnetic storage media. So far the grain isolation is a problem while using thin film magnetic storage media. Further, during miniaturization, superparamagnetic limit is reached due to increasing thermal effects at this scale which makes the magnetic grains of magnetic nanowires susceptible to thermal fluctuations. To overcome this problem of superparamagnetism and grain isolation, nanowires with high coercivity, remanent magnetization and thermal stability are thought to be the alternatives. Alloy and multilayered magnetic nanowires prepared by some less expensive technique with suitable magnetic and thermal properties can serve to overcome this challenge. [ABSTRACT FROM AUTHOR]

The nature of magnetic ordering of spin-clusters in the naturally grown bilayerd Brownmillerite compound Ca2.4La0.1Sr0.5GaMn2O8 has been studied by dc magnetization technique as a function of both temperature and magnetic field. The behavior of M(T) curves suggests a spin freezing at lower temperatures. With increasing applied magnetic field, the freezing temperature Tg (H) decreases and follow the well known Almeida-Thouless (AT) nature Tg∞H2/3 for low field. The freezing temperature at zero field Tg(0) was found to be 90 K. The temperature as well as field dependent magnetization study suggest a spin-glass type nature of the clusters. [ABSTRACT FROM AUTHOR]

Superparamagnetic properties of iron-oxide nanoparticles paved the way for various biomedical applications, such as magnetic resonance imaging (MRI), magnetic targeting of drug vectors or magnetically-induced therapeutic hyperthermia. Living cells interact with nanoparticles by internalizing them within intracellular compartments, called lysosomes. In the course of cellular uptake, the spatial distribution of magnetic nanoparticles changes from dilute isolated nanoparticles to a highly concentrated assembly of nanoparticles confined in micrometric lysosomes. This local organization of nanoparticles, which is induced by the intracellular environment, may have important consequences for their superparamagnetic behaviour. In particular, it may deeply affect their magnetic properties used for biomedical purposes and therefore must be considered when optimizing the properties of nanoparticles for a peculiar application. In this paper, we review the role of intracellular confinement of nanoparticles for their three main biomedical uses: MR cellular imaging, magnetic targeting of cells and magnetically induced hyperthermia. [ABSTRACT FROM AUTHOR]

We present a new method for probing wettability of rock/oil/brine systems using nuclear magnetic relaxation dispersion (NMRD). Unlike conventional transverse relaxation studies, this approach gives a direct probe of the dynamical surface affinity of fluids, thus allowing the separation of wetting from non-wetting fluids through their typical NMRD features. To quantify these features we introduce a microscopic dynamical surface affinity index which measures the dynamical correlation (i.e. microscopic wettability) between a diffusive fluid and fixed paramagnetic relaxation sources at the pore surfaces. We apply this technique to carbonate reservoir rocks of bimodal porosity saturated with oil (Sw = 0%), brine (Sw = 100%) and mixture of oil/brine (Swirr). [ABSTRACT FROM AUTHOR]

Thermal fluctuation effects in magnetophoresis of commercial superparamagnetic beads are analyzed. By tracking the trajectories of the beads the distribution functions of their displacements in two perpendicular directions are determined. This allows us to determine simultaneously the mean velocity of the beads and their diffusion coefficient. Magnetic moment of a single bead is found by applying the Einstein relation. Distribution of the magnetic moment values are analyzed for two commercial samples of the superparamagnetic beads. [ABSTRACT FROM AUTHOR]

Recently, magnetic particle imaging (MPI) has been presented as a new method for the measurement of the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIONs). MPI is based on the nonlinear magnetization response of nanoparticles that are subjected to a sinusoidal magnetic field. Spatial resolution and signal to noise ratio of MPI depend on the particle quality. This is particularly important when stem cells shall be tracked with MPI. Stem cell-based treatment is an upcoming technology in targeted cancer-therapy. In this study, we analyzed the particle quality of newly developed dextran-coated SPIONs-with respect to their response in the imaging experiment-using magnetic particle spectrometry. The uptake of dextran-coated SPIONs into rat and human adult stem cells was monitored via transmission electron microscopy. Furthermore, adult stem cells were incubated with FITC-dextran-coated SPIONs and stained for confocal laser scanning microscopy. The dextran- and FITC-dextran coated SPIONs were localized in the cytoplasm of rat and human adult stem cells. MPI promises real-time imaging with high spatial resolution at high sensitivity. Our data support iron oxide loaded adult stem cells as a powerful tool for targeted cancer therapy. [ABSTRACT FROM AUTHOR]

The new magnetic reactor based solid phase synthesis strategy allows magnetic immobilization of nanoparticles in order to perform the derivatization step(s) with relevant biomolecules on the immobilized magnetic nanoparticles. Monoclonal Mouse anti-Human CD11b shows affinity toward monocyte/macrophage integrin MAC-1 (CD11b/CD18) which is involved in leukocyte adhesion and functions as a cell receptor and was coupled on superparamagnetic iron oxide nanoparticles (SPIONs) in this reactor. The resulting anti-CD11b derivatized SPIONs were analyzed and compared to conventionally derivatized SPIONs. The reactor-derivatized anti-CD11b-SPIONs show enhanced colloidal stability during and after the surface derivatization steps. The yield and quality of the resulting particles can also be significantly improved in terms of reaction time and yield, particle size distribution, and scalability by using this magnetic reactor. These highly specific particles were successfully used in imaging studies of monocytes. [ABSTRACT FROM AUTHOR]

Presently much attention is given to RF hyperthermia with superparamagnetic particles. Usability of high-coercive ferromagnetic particles and strong audio-frequency fields still remains dim and is called in question. In this paper we analyze prerequisites of feasible low-frequency magnetic hyperthermia, present suitable magnetic particles, computerized equipment for experiments with small animals, and results of controlled low-frequency treatment of model tumors on rats. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles belong to the most promising nanosized objects for biomedical applications. However, little is known about clearance of magnetic nanoparticles from the organism. In this work superparamagnetic iron oxide particles fluidMAG-ARA were injected into tail vein of mice at a dose of 17 mg per 20 g body weight. At various time intervals after the injection the mice were sacrificed and their organs collected. A Mössbauer study allowed to detect magnetic particles in the liver and spleen and showed the degradation of the particles with incorporation of exogenous iron into paramagnetic ferritin-like iron species. [ABSTRACT FROM AUTHOR]

We have developed a modified synthetic protocol for the growth of monodispersed, superparamagnetic, flower-like colloidal nanoclusters (CNCs) with 40-120 nm average diameters. Importantly, these are consisted of smaller iron oxide nanocrystals, also with adjustable size (12.2-7.7 nm). We show that their optical properties can be tuned by applying an external magnetic field. Spectrophotometric measurements under these conditions reveal a diffuse reflectance maximum in the visible range, which is related to the CNCs assembly in ordered structures. The increasing field strength leads to a blue shift in the spectral weight when the size of the CNCs is above a critical diameter. The size-dependent characteristics of the CNCs determine their magneto-optical behavior and their potential in photonic crystal based technologies. [ABSTRACT FROM AUTHOR]

Ultrasmall superparamagnetic particles of iron oxide have a variety of clinical applications as contrast agents in molecular and cellular magnetic resonance imaging. Physicochemical parameters such as size, surface charge, coating dramatically influence their pharmacokinetic behaviour and, hence their potential clinical applications. From an industrial point of view, specifications such as stability in biologic media are crucial to avoid failure during the development of these contrast agents. [ABSTRACT FROM AUTHOR]

LiYF4 crystal doped with rare earth ions has numerous optical applications due its properties like a wide range transparency, low value of induced nonlinear refractive index, optical and thermal stability. The energy levels and wave functions of Nd3+ and Er3+ ions doped in LiYF4 host has been obtained by diagonalizing the corresponding crystal field Hamiltonian. They are used to compute the temperature dependence and anisotropy of the molar paramagnetic susceptibility. From the results of calculations, the Curie constants and Jahn-Teller stabilization energy for both ions in LiYF4 are evaluated. Comparison with experiment shows that the results are quite satisfactory. [ABSTRACT FROM AUTHOR]

Both superparaelectric and superparamagnetic behaviour has been observed in rare earth magnetic ion Gd3+ doped Lead Magnesium Niobate (Gd-PMN). Field induced polarization and magnetization studies reveal hystresis loss free P-E and M-H loop at 300K and 5K, respectively. Temperature dependence of inverse susceptibility plot shows deviation at a temperature "td" when fitted with the Curie-Weiss law. This deviation has been attributed to transition from paramagnetic to superparamagnetic behaviour as reported in amorphous Pd-Ni-Fe-P alloys. [ABSTRACT FROM AUTHOR]

CoFe2O4 and ZnFe2O4 nanoparticles were synthesized by modified and cost effective sol-gel autocombustion method. X-ray diffraction study confirms the spinel phase formation of face centered cubic lattice with space group Fd3m and without any impurity. Magnetic measurements demonstrate that the CoFe2O4 shows saturation magnetization of 2.73 µB/f.u. where as ZnFe2O4 shows paramagnetic behavior. Magnetic behavior of CoFe2O4 and ZnFe2O4 is confirmed from Mössbauer studies. Effect of sintering on structural, magnetic and cation occupancy of substituted cobalt ferrite is discussed in this paper. [ABSTRACT FROM AUTHOR]

Nanocomposite of Fe nanoparticles with activated carbon has been synthesized to alter the magnetic spin-spin interaction and hence study the dilution effect on the static and dynamic magnetic properties of the Fe nanoparticle system. Transmission electron microscopic (TEM) image shows the spherical Fe nanoparticles dispersed in carbon matrix with 13.8 nm particle size. Temperature dependent magnetization measurement does not show any blocking temperature at all, right up to the room temperature. Magnetic hysteresis curve, taken at 300K, shows small value of the coercivity and this small hysteresis indicates the presence of an energy barrier and inherent magnetization dynamics. Langevin function fitting of the hysteresis curve gives almost similar value of particle size as obtained from TEM analysis. Magnetic relaxation data, taken at a temperature of 100K, were fitted with a combination of two exponentially decaying function. This diluted form of nanoparticle system, which has particles size in the superparamagnetic limit, behaves like a dilute ensemble of superspins with large value of the magnetic anisotropic barrier. [ABSTRACT FROM AUTHOR]

We have studied some curious effects of an external perturbation on the temperature-dependent field-cooled cool-down magnetization response (MFCC (T)) in a single crystal of a low Tc (≈ 7.10 K) superconductor Ca3Ir4Sn13. The MFCC (T) response in the superconducting state (just below Tc) of this compound shows anomalous paramagnetic magnetization signal(s). In the field-temperature (H-T) region wherein the paramagnetic magnetization occurs in Ca3Ir4Sn13, a perturbation applied to the system in the form of an impulse of an ac magnetic field results in an unpredictable switching of the magnetization from a given paramagnetic value to a diamagnetic or to a different paramagnetic value. The magnetization response is thus found to be multi-valued at a given (H,T) value. The MFCC (T) curves are found to be path-dependent below Tc. Surprisingly, our results obtained in a bulk type-II superconductor Ca3Ir4Sn13 resemble strongly with the characteristics of the magnetization behavior anticipated for the giant vortex states with multiple flux quanta (LΦ0, Φ0 = hc/2e, L > 1) known to occur in the mesoscopic-sized superconductors. [ABSTRACT FROM AUTHOR]

Nanohybrid multiferroic core-shell structures of MgFe2O4@BaTiO3 with magnetic core and ferroelectric shell possessing bifunctional properties were synthesized. The hybrid composite, with MgFe2O4 core of smaller diameter, exhibited bifunctional properties including superparamagnetism with a blocking temperature near 50K and ferroelectricity at ambient conditions. The multiferroic MgFe2O4@BaTiO3 core-shell sample exhibit typical magnetic field control of electric properties demonstrated by the magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

Nanoparticles of Mg0.5Zn0.5Fe2O4 ferrite have been synthesized by co-precipitation method. XRD and Mössbauer spectroscopic results of Mg0.5Zn0.5Fe2O4 annealed at 200 °C, 500 °C and 800 °C are reported. It was observed that the crystallite size increases and the lattice parameter decreases with increase in annealing temperature. The observed decrease in lattice strain supports the increase in crystallite size. The Mössbauer spectra of the samples annealed at 200 °C and 500 °C exhibits superparamagnetic doublets whereas the Mössbauer spectrum of the sample annealed at 800 °C exhibits paramagnetic doublet along with weak sextet of hyperfine interaction. The values of isomer shift resemble the presence of high spin iron ions. The studied ferrite nanoparticles are suitable for biomedical applications. The results are incorporated employing core-shell model and cation redistribution. [ABSTRACT FROM AUTHOR]

Monodisperse nickel nanoparticles (Ni-NPs) were synthesized via a thermal decomposition process. The NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). They were spherical with mean diameter of 4 nm. Zero field cooled (ZFC) and field cooled (FC) magnetization versus temperature data displayed interesting magnetic interactions. ZFC showed a peak at 4.49 K, indicating the super paramagnetic behavior. Magnetic anisotropic constant was estimated to be 4.62x105 erg/cm³ and coercive field was 168 Oe at 3 K. [ABSTRACT FROM AUTHOR]

Spin switching devices constructed using self-assembled magnetic Ge quantum dots are the ultimate goal of this effort. These devices are based on the manipulation of magnetic exchange between magnetic quantum dots and/or coherent spin states in the quantum dots. In this study, we introduced 1.1 atomic % of Mn ions into Ge thin films and 3 at.% Mn into Ge Quantum Dots by ion implantation in order to explore the ferromagnetism in Mn implanted Ge. In order to recrystallize the Ge and enhance the incorporation of Mn ions into the Ge lattice, rapid thermal annealing was applied following the implantation. A maximum saturation moment of 0.7 μB/Mn at 5 K was reached when the sample was annealed at 300° C and the moment decreased with higher annealing temperatures. The ferromagnetism in Mn:Ge thin films disappeared at ∼15 K. However, superparamagnetism has been observed at 1 T up to 200 K for the 300° C annealed film and persisted to room temperature for the 400° C annealed film. Mn implanted Ge Quantum Dots were also found to be ferromagnetic at low temperatures and showed a superparamagnet transition around 200 K. [ABSTRACT FROM AUTHOR]

The PASER [1] (Particle Acceleration by Stimulated Emission of Radiation) concept for particle acceleration entails the direct transfer of energy from an active medium to a charged particle beam. The PASER was originally formulated for optical (laser) media; we are planning a PASER demonstration experiment based on an optically pumped X-band paramagnetic medium consisting of porphyrin or fullerene (C60) derivatives in a toluene solution or polystyrene matrix. We discuss the background of this project and report on the status of the experiment to measure the acceleration of electrons using the microwave PASER. [ABSTRACT FROM AUTHOR]

These lecture notes give an introduction to quantum magnetism. We start by a discussion of paramagnetism and the Weiss meanfield theory applied to the Ising model. In the following sections, we turn to the fully quantum-mechanical Heisenberg Hamiltonian. First, we consider the limit of small clusters whose properties we analyze via exact diagonalization. Bulk quantum magnets are then within the framework of the linear spinwave theory. A short discussion of Monte Carlo techniques follows. Finally, we discuss aspects of entanglement in quantum spin systems. [ABSTRACT FROM AUTHOR]

The role of boundary corrections to Landau diamagnetism for macroscopic free electronic systems has been discussed [1–8], and orbital paramagnetic effects have been experimentally observed in small systems [9]. The correction terms can theoretically be either paramagnetic or diamagnetic depending on the increase in potential energy at the surface which defines the perimeter of the electron system. In this work calculations of orbital magnetism have been performed for nanometer scale 2DEG strips laterally confined by an attractive transverse parabolic potential. The emergence of orbital paramagnetism depends sensitively on areal electron density, strip width, and parabolic potential strength such as may be produced by a split gate with negative voltage applied. Selected graphical results display considerable variation in the orbital paramagnetic contribution compared to the Landau diamagnetic susceptibility. [ABSTRACT FROM AUTHOR]

The magnetic susceptibility and thermoelectric power of Zr0.9Ti0.1CrxFe2-x intermetallic compounds were investigated as functions of hydrogen content. The alloys are paramagnetic, with magnetic susceptibility and Seebeck coefficient increasing with the amount of stored hydrogen. The susceptibility is proportional to the Seebeck coefficient and to the d-electron concentration, consistent with a free-electron model. The susceptibility of alloys with lower iron concentration suggests exchange-enhanced Pauli paramagnetism. However, Curie-Weiss paramagnetism likely coexists in alloys with higher iron content. Magnetic and electronic measurements may be used to assess the ability of an alloy to store hydrogen. [ABSTRACT FROM AUTHOR]

We present a review on using a statistical mechanics-based model for calculating magnetic properties of hexagonal, cubic and mixed-anisotropy systems. Although our simple model is not as elaborate as, for example, monte carlo simulation it demonstrates a success in producing all the major features of magnetization curves of the ferromagnetic systems studied. Examples of these features are sequence of easy-axes of magnetization, spin reorientation and superparamagnetism in small particles. The magnetization curves, magnetic susceptibility and orientation probability of the magnetization vector are calculated in a wide range of temperature, particle size and magnetic field. Examples of the systems we report are unaxial ferromagnets e.g. Gd, PrCo5 and Nd2Fe14B; cubic materials e.g. Fe and Ni and mixed-anisotropy systems, e.g. Fe on stepped Ag (001) substrates, in which a jump in the magnetization is found to depend on the ratio of the uniaxial to biaxial anisotropy present in these systems. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The 1H and 13C NMR as well as the X-band and high-field EPR spectra of TDAE-C70 are compared with those of TDAE-C60. The observation of a weak temperature dependent high-field EPR line below 50 K may be connected with the occurrence of a ferromagnetic modification of TDAE-C70 in addition to the well known paramagnetic one. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Magnetite loaded polyvinyl alcohol and polystyrol hydrogels were investigated by the help of 57Fe Mössbauer spectroscopy, XRD and transmission electron microscopy. Chemically cross-linked polyvinyl alcohol hydrogels filled with magnetite particles were prepared from magnetite sol obtained from FeCl2 and FeCl3 in aqueous solution. At near room temperature, the Mössbauer spectrum has hyperfine fields smaller than those characteristic of bulk magnetite. The temperature dependent collapse of the hyperfine splitting can be associated with paramagnetism rather than superparamagnetism. This indicates that a special magnetic interaction occurs between the small particles. This may be interpreted in the terms of dynamic magnetic phenomenon in fine particle magnetite incorporated into swollen elastic polymer network by supposing magnetic ordering of clusters (after Boquet et al.) created by high concentration of defects when the hyperfine field distribution is mainly influenced by the slow relaxation of the magnetic moments of the clusters. Nevertheless, the effect of monodispersity of the colloid system may also contribute to the unusual relaxation shape of the Mössbauer spectra. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

In order to provide continuous cooling at 50 mK for space or laboratory applications, we are designing a miniature adiabatic demagnetization refrigerator (MADR) anchored at a reservoir at 5 K. Continuous cooling is obtained by the use of several paramagnetic pills placed in series with heat switches. We aim at a fast cycling process (≈ 500 s) in order to reduce the size of the pills. For that purpose, we developed and tested magnetoresistive heat switches based on single crystals of tungsten. They provide good thermal performance for a very short switching time, depending only on the ramping speed of the magnet used. Magnets for cycling the pills and the heat switches are made from high current density NbTi wires. High permeability materials are used to shield these magnets, which is crucial to minimize stray magnetic fields. The field in the heat switch magnets is maximized using a holmium core. The magnets have been modelled using a numerical simulation. Small magnets(≈ 100 cm3) with an operating field of 3 T have been designed and tested with a ramping time of less than 30 s. We have tested a single-stage MADR with a small pill, magnetoresistive heat switch and fast cycling time. These tests confirmed the feasibility of our design. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report on the magnetic properties of Li-doped Mo-S nanotubes (NTs), which appears to be a realisation of a near-ideal 1D strongly correlated state in a bulk system. The material is exceptional because of its inherently extraordinarily weak coupling between 1D subunits, which is an order of magnitude weaker even than in carbon nanotube ropes. In spite of clear evidence for strong electronic correlations from a giant paramagnetic susceptibility, no transition to an ordered state is observed down to very low temperatures. Instead,the system appears to be stabilised in a paramagnetic state by fluctuations characteristic of 1-dimensional systems, with no evidence of a quantum critical point as T = 0 is approached. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

New paramagnetic susceptibility thermometers have been developed for use in fundamental physics missions in earth orbit. These devices use a SQUID magnetometer to measure the variation in the dc magnetization of a thermometric element that consists of a dilute concentration of manganese in a palladium matrix. Near 2.2 K these new PdMn thermometers have demonstrated a temperature resolution of better than 100 pK/[Square_Root]Hz and a time constant of 50 ms when operated with a 50 K/W thermal resistance to the liquid helium sample. These thermometers have been observed to be remarkably stable, with a drift of less than 10 fK/s. The observed power spectral density of the noise from these thermometers is consistent with separate measurements of the device’s time constant and thermal standoff from the bath. Recently these PdMn materials have been made into thin films and microstructures for use in future studies of quantum liquids, and for possible use in a new class of bolometers and radiometers. These thermometers have been integrated into an experimental cell and thermal isolation network that are adequate to keep stray heats stable to within a few picowatts, with no systematic temperature errors greater than 60 pK, over the course of a planned fundamental physics experiment on Earth orbit. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

We describe the current status of the experiment at Sussex to measure the electron's permanent electric dipole moment de using the paramagnetic molecule YbF. We consider a number of systematic effects which could mimic de and conclude that they are far below the current experimental sensitivity. As of June 2001 we have accumulated over 20 hours of data, which combined give a measurement d[sub e] = 0.6 ± 4 ×10[sup -26] = e.cm. [ABSTRACT FROM AUTHOR]

I give a brief introduction to Luttinger liquids. Luttinger liquids are paramagnetic one-dimensional metals without Landau quasi-particle excitations. The elementary excitations are collective charge and spin modes, leading to charge-spin separation. Correlation functions exhibit power-law behavior. All physical properties can be calculated, e.g. by bosonization, and depend on three parameters only: the renormalized coupling constant K[sub ρ], and the charge and spin velocities. I also discuss the stability of Luttinger liquids with respect to temperature, interchain coupling, lattice effects and phonons, and list important open problems. [ABSTRACT FROM AUTHOR]

The nanosized Ni0.3Zn0.7Fe2O4 (~ 15 nm) has been synthesized by high energy ball milling of the bulk powder sample. The sample has been characterized by powder x-ray diffraction, field emission and transmission electron microscopic and dc magnetic measurement techniques. The dc magnetic measurement on the sample indicates that the sample exhibit enhancement of magnetization compared to its counterparts synthesized by chemical methods. Moreover, the system stores the memory of either decrease or increase of magnetic field enabling a magnetic coding of "0" and "1" which can be profitably used in magnetic storage and sensing devices. [ABSTRACT FROM AUTHOR]

In the present manuscript, MnxCo1-xFe2O4 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanoparticles have been synthesized with co-precipitation method by annealing at 900 °C and studied the structural and magnetic properties. X ray diffraction pattern reveals the formation of single phase cubic spinel structure with the space group Fd-3m. An impurity peak of a-Fe2O3 has been observed in the XRD patterns of samples with Mn composition, x ≥ 0.4. However, this impurity phase of a-Fe2O3 is not observed in the MnFe2O4 sample synthesized by annealing at 500 oC. FESEM results indicate the formation of nano-sized particles. Magnetic measurements show ferrimagnetic interaction in MnxCo1-xFe2O4 (x≥0) nanoparticles at room temperature. However, MnFe2O4 sample synthesized by annealing at 500 °C shows superparamagnetic behavior. We have fitted the M-H curve of MnFe2O4 synthesized by annealing at 500 °C with modified Langvenin function to confirm superparamagnetism .The correlation between the structural and observed magnetic properties of as synthesized samples nanoparticles will be described and discussed in this paper. [ABSTRACT FROM AUTHOR]

Nanosized Co0.3Zn0.7Fe2O4 having average particle size ~20 nm has been synthesized by mechanochemical method. The results of dc magnetic and Mössbaeur studies suggest that the sample is ferrimagnetic in nature and shows superparamagnetic behavior above 230K. Magnetic ordering in the sample evolves gradually upon cooling the system below blocking temperature. Moreover, the sample exhibits enhancement of magnetic order and ordering temperature with respect to its counterpart synthesized by chemical routes mainly due to increase of stress anisotropy induced by high energy ball milling. We have shown that maintaining suitable cation distribution helps in enhancement of magnetization by reducing the adverse effect of spin canting. [ABSTRACT FROM AUTHOR]

We report time differential perturbed angular distribution measurement of 54Fe on a polycrystalline EuFe2As2 sample. The local susceptibility measured shows Curie-Weiss like temperature dependence in the paramagnetic region. The spin-lattice relaxation observed shows Korringa like relaxation and changes discontinuously at TS = TN = 190 K. Below TN, the hyperfine field shows two components. The low filed component of the hyperfine field shows a power law dependence of 0.27 on temperature. [ABSTRACT FROM AUTHOR]