Magnetic Susceptibility Investigations Research Articles

Time domain study of Brownian and Néel relaxation in ferrofluids

Relaxation of six ferrofluids differing in particle size was studied using a dc SQUID magnetometer. We observed Néel relaxation with nonlinear ln( t) behaviour in freeze-dried samples and viscosity-dependent Brownian relaxation in glycerol-based dried samples. Investigations of the basic magnetic parameters, complex susceptibility and remanence complement the time-dependent measurements.

Mono- and polynuclear schiff base complexes derived from polyoxadiamines

New compartmental macroacyclic and macrocyclic Schiff bases have been prepared by reaction of the formyl precursors 2,3-dihydroxy-benzaldehyde, 3-methoxy-2-hydroxy-benzaldehyde and 2,6-diformyl-4-chlorophenol with 1,2-diaminoethane, 1,3-diaminopropane and the polyethyleneoxy-diamine H 2N(CH 2) 2[O(CH 2) 2] nNH 2 ( n = 1, 2, 3) also with the presence of a templating ion. In these ligands the shape of one or borh compartments has progressively been enlarged and the denticity increased in order to link up to four metal ions into the coordination moiety. These ligands react with copper(II), nickel(II) or lanthanide(III) salts to form mononuclear, homo- and heterodinuclear, homotrinuclear or homotetranuclear complexes. The ligands and the complexes were characterized by elemental analysis, IR, 1H and 13C NMR, mass spectrometry, magnetic susceptibility and SEM investigations.

Hg1-xCoxSe mixed crystals: new semimagnetic semiconductor

Results of infrared reflectivity (in the phonon and plasma edge spectral regions) and magnetic susceptibility investigations performed on Hg1-xCoxSe samples corresponding to a wide range of the crystal compositions (0 < x < 0.05) are presented and discussed. The evidence of an acceptor character of Co impurity is shown. Antiferromagnetic interactions between Co2+ are confirmed, effective exchange integral is estimated to be Jd-d/kB = (−61.3 ±6.7) K.

Synthesis, X-ray diffraction and AC magnetic susceptibility investigations of HgBa 2CuO 4+ δ

HgBa 2CuO 4+ δ compound is synthesized from the solid state reaction of the precursors Ba 2CuO 3 and HgO. The structure and the crystallite size are determined using the X-ray diffraction technique. The crystallite size depends on the reflecting plane ( hkl) and the average size is ∼ 90 nm. The superconducting transition temperature T c and the irreversibility line are determined from AC magnetic susceptibility measurements in magnetic fields up to 1 T. The T c value of the compound is 95.3±0.5 K.

Susceptibility and NQR investigations on NaCuO 2

Crystalline samples of NaCuO 2 have been synthesized and characterized by magnetic susceptibility and 23Na-NMR investigations. Furthermore, a 63Cu-NQR line at 37.48 MHz (4.2 K) could be detected. This frequency is higher than all 63Cu-NQR frequencies found so far in high- T c superconductors, which is in coincidence with the high formal valence of 3+ in NaCuO 2.

Crystal-field excitations in CeCu2Si2.

An inelastic-neutron-scattering investigation of the dynamic magnetic susceptibility of the heavy-fermion compound CeCu 2 Si 2 is presented. We find evidence for only one crystal-field (CF) transition at 30 meV in addition to quasi-elastic-scattering implying a doublet-quartet level scheme in agreement with specific-heat results but in contradiction with two earlier neutron-scattering studies. Using other experimental results, we propose a set of CF parameters (B 2 0 =-1.29±0.06 meV, B 4 0 =(-4.3±0.2)×10 -3 meV, |B 4 4 |=0.45±0.02 meV) which describe satisfactorily all the measured properties that depend on the CF

Structure and superconductivity of YBa2Cu3O7-x-BaTiO3composites

Abstract Bulk and film samples have been prepared of composite YBa2Cu3O7-x-BaTiO3. The X-ray diffraction, SHG, resistivity and magnetic susceptibility investigations have been performed. The superconductive phase transition is broadened towards lower temperatures in the presence of BaTiO3, the resistivity of the normal phase being increased. Changes in behaviour of the composite films can be partly explained by weak contacts between particles of YBa2Cu3CV7-x during the preparation.

Exchange interaction in trinuclear transition-metal complexes

Heterotrinuclear transition-metal complexes are of interest for the study of long-range magnetic interactions and as model compounds for the investigation of biological electron transport chains. The systems under study here contain paramagnetic Fe111-containing terminal units and a bridging unit with M11=Zn, Cu, Ni, Co, Fe, Mn. The spectroscopic methods applied include Mossbauer, — EPR- and magnetic susceptibility investigations. The spin-Hamiltonian analysis of the measured results yields information about the intramolecular super-exchange interactions among the various magnetic transmition-metal sites. In view of the 7A separation between the two terminal Fe111 sites, the Fe111...Fe111 exchange coupling of the order −10cm−1 is large.

Critical behaviour near the magnetic percolation threshold

Detailed investigation of the initial magnetic susceptibility of Fe x Ni 80− x B 18Si 2 alloys with concentrations ( x=2.5, 2.6, 2.7 and 2.8) in the vicinity of the magnetic percolation threshold ( x≈2.4) has been performed. High sensitivity ac susceptibility measurements in a very small driving field show that disorder does not affect the critical behaviour of amorphous ferromagnet in the immediate vicinity of T c, but manifests itself in a broader range above T c.

Magnetic susceptibility, EPR, Moessbauer, and x-ray investigations of heteropolynuclear clusters containing iron(III) and copper(II) ions: {Cu(Mesalen)}2 Fe(acac) (NO3)2 and {Cu(Mesalen)}3 Fe(acac) (PF6)2

Magnetic susceptibility, EPR, Moessbauer, and x-ray investigations of heteropolynuclear clusters containing iron(III) and copper(II) ions: {Cu(Mesalen)}2 Fe(acac) (NO3)2 and {Cu(Mesalen)}3 Fe(acac) (PF6)2

Moessbauer and magnetic susceptibility investigation of a ferromagnetically coupled iron(III) porphyrin-dicopper(II) system with imidazolate bridging ligands

Susceptibility and Mossbauer techniques were employed to analyze the magnetic properties of the trinuclear complex [Fe III -(TPP)(CuIM) 2 ]B 11 CH 12 •5THF (TPP=tetraphenylporphyrinate; CuIM=copper(II) complex of the Schiff base formed by sequential condensation of 5-chloro-2-hydroxybenzophenone, 1,2-diaminobenzene, and imidazole-4-carbaldehyde). The Fe(II) analogue (magnetic Fe(III) ions replaced by diamagnetic Fe(II) ions) and its Ni analogue (magnetic Cu ions replaced by diamagnetic Ni ions) were studied

The Faraday Effect of Rare-Earth Ions in Garnets

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Magnetic properties of REAl 6Fe 6 compounds for RE ≡ Y, Dy and Ho

Investigations of magnetostriction, magnetization, magnetic susceptibility and electrical resistivity of the tetragonal compounds REAl 6Fe 6 (RE ≡ Y. Dy and Ho) are presented. It was ascertained that the anisotropic magnetostriction is connected with the rare earth sublattice. With decreasing temperature an increase in anisotropic magnetostriction and hysteresis loop was observed.

Superconductivity in the Bi-Sr-Ca(Y,Gd)-Cu-O system: DC magnetic susceptibility and microwave absorption investigations

Microwave absorption and DC magnetic susceptibility measurements are carried out on Bi 2Sr 2Ca 2− x Re x Cu 2O y (RE=Y, Gd; x=0, 0.25 and 0.5). These studies clearly establish the correlation between conventional DC magnetic susceptibility and changes in microwave reflectivity/absorption as the sample is cooled through the superconducting transition temperature ( T c). The results indicate that T c, as determined by both the methods, initially increases with x, though for higher concentrations of x, superconductivity is suppressed. The Curie-Weiss temperature is found to increase with increasing concentration of Gd. No evidence for the local moment of Cu 2+ is found in the EPR measurements. The EPR of Gd 3+ is observable below 30 K for x=0.5 with a possible evidence for crystal-field interaction. Absence of Gd 3+ EPR signal at higher temperatures, and also for x=0.25, might imply extra pathways for spin-lattice relaxation.

Magnetic susceptibility investigations of the La 2NiO 4+δ system

Magnetic susceptibility studies were performed on La 2NiO 4+δ in the temperature range between 300 K and 1100 K as a function of composition, δ. Samples with nearly ideal stoichiometric ratios ( δ = .002) show a previously unreported transition to antiferromagnetic order which occurs in the same temperature range as the semiconductor-metal transition. An increase in δ leads to a suppression of the magnetic ordering temperature while the transition in resistivity remains unaltered. This result is interpreted in terms of an oxygen interstitial defect mechanism and the quasi-two-dimensional structure of the material.

ChemInform Abstract: Electron Paramagnetic Resonance and Static Magnetic Susceptibility Investigations of Solid Solutions of Manganese in β‐Rhombohedral Boron

Abstractare performed in the temp. range 3.6‐300 K for samples containing 0.03‐1.82 at.% Mn.

Electron paramagnetic resonance and static magnetic susceptibility investigations of solid solutions of manganese in β-rhombohedral boron

The magnetic properties and the distribution of manganese atoms in the β-rhombohedral boron structure were studied using electron paramagnetic resonance and static magnetic susceptibility measurements in the temperature range 3.6−300 K. Solid solutions with a manganese concentration in the range 0.03–1.82 at.% were studied. The manganese atoms occupy three different crystallographic positions with g values of 2.54, 3.32 and 4.48. With increasing manganese content the spins interact and form clusters and at the highest manganese content cluster-cluster interaction is observed. The distribution of the manganese atoms among the available crystallographic positions depends on the concentration. At the highest concentrations studied the ratio between the occupancies of the different holes is almost constant.

Magnetic susceptibility and structural investigations of REAl 6Fe 6 compounds for RE = Y, Gd, Tb, Dy, Ho and Er

Mesure par la methode de Faraday de la susceptibilite magnetique entre la temperature de Curie et 900 K. Determination a partir de ces resultats du moment paramagnetique effectif et de la temperature de Curie paramagnetique. Influence du champ magnetique applique. Les resultats sont en accord avec le comportement de verre de spin suggere pour ces composes

Single-crystal magnetic susceptibility and crystal-field investigation of terbium phosphate in the tetragonal phase

The dc magnetic susceptibility of TbPO 4 in the tetragonal phase has been measured from room down to liquid nitrogen temperatures for external field orientations both perpendicular and parallel to the c-axis. The crystal field derived earlier from an analysis of the observed spectra was revised to take into account intermediate coupling effects which yielded a lower rms deviation with the experiment. A fairly good theoretical explanation of the magnetic behavior of Tb 3+ in TbPO 4 observed by us and other workers over a wide range of temperature (300−4 K) was obtained using the revised crystal field and taking the internal field through mean-field approach. The electronic heat capacity is computed which shows two Schottky anomalies one at ∼10 K and the other at ∼55 K in partial agreement with available experimental information. The interaction of the nuclear spin with the electric field gradient and the hyperfine magnetic field is studied; an anomaly in the nuclear heat capacity is located at ∼70 mK.

Static magnetic susceptibility of Zn1-xMnxSe.

We present results of an investigation of the static magnetic susceptibility of ${\mathrm{Zn}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Se for x=0.05, 0.15, 0.30, and 0.45. From the Curie-Weiss behavior of the susceptibility at high temperatures, we determine the effective Mn-Mn exchange constant ${J}_{1}$ to be -13.5\ifmmode\pm\else\textpm\fi{}0.95 K. By using the results of our study in conjunction with direct measurements of the nearest-neighbor exchange integral ${J}_{\mathrm{NN}}$ from inelastic neutron scattering by nearest-neighbor pairs, we obtain an estimate of the next-nearest-neighbor exchange constant ${J}_{2}$=-2.4 K.