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Pure o-LiMnO2 prepared by solid state reaction under Ar flow at 850 °C crystallizes in an orthorhombic symmetry (SG: Pmnm). Mn3+ with four unpaired electrons is subjected to a strong Jahn-Teller (J-T) distortion, where the MnO6 octahedron is significantly elongated (1.17%) along the c axis. In air, the oxide converts to spinel LiMn2O4 at ∼320 °C. The magnetic susceptibility of LiMnO2, measured between 4.2 and 900 K, indicates a long range order. The negative θP value (−790 K) reveals strong antiferromagnetic interactions between half-filled dz21 orbital. The predominant interaction is negative and occurs between Mn3+ and its next-nearest neighbors via O2− ions by super exchange with Mn3+-O: 2p-Mn3+ angle of 178°. Above 300 K, the susceptibility follows a Curie Weiss law with a magnetic moment of 5.26 μB consistent with the high spin state Mn3+ (t2g3 eg1) but slightly larger than the spin only contribution for the ground state 5Do. The susceptibility is field dependent down to 4.2 K and a spin canting has been detected at low temperature. As magnetic chains are separated by non-magnetic Li ones, the interactions are confined along the [1 1 0] direction and one can expect a good realization of one dimensional model. Therefore, the magnetic data have been fitted on the base of the isotropic model for finite linear chain in terms of intra-chain antiferromagnetic interactions using the Fisher model. The best fitting is obtained for a value of J/k = −60 K. The results are compared with those of the crednerite CuMnO2 with smaller J/k value (−33 K).

Delafossite compound, CuCrO2, popularly known as transparent conducting oxide, has previously been reported to demonstrate antiferromagnetic ordering of the triangular magnetic lattice below 24 K. We find that mere 5% Ti-substitution at Cr-site, leads to short range magnetic correlations, manifested as non-analytical behaviour of H/M and other anomalies in the low magnetic field dc magnetization, ac magnetic susceptibility, time dependent magnetization, and isothermal remanent magnetization. The ac susceptibility measured at different applied frequencies do not show any frequency dependence, ruling out the glassy magnetic phase. The short-range magnetic correlations are observed over a wide temperature range starting from 180 K and below, until the system orders antiferromagnetically at 22 K. These correlations which are most pronounced at low values of applied magnetic field, get readily suppressed when the fields exceed 0.5 T. Signatures associated with these short-range correlations seem to fit a Griffiths-like phase description. The results of heat capacity measurement with and without magnetic field, provides additional information about the dimensionality of the magnetic interactions. Rietveld refinement of the X-ray diffraction data reveals that the highly anisotropic crystal structure remains unaffected with the substitution. A static disorder driven magnetic inhomogeneity arising in the triangular magnetic sublattice of Cr ions decreases the dimensionality of magnetic interactions, and seems to be the possible origin of this interesting magnetic behaviour.

The binding energy of a hydrogenic-like donor complex D 0 placed in a two-dimensional Gaussian quantum dot GaAs semiconductor is determined incorporating the Rashba and Dresselhaus spin-orbit interactions in the presence of an externally applied magnetic field. A unitary transformation is employed to deal with the spin-orbit interactions and their effects are incorporated up to second order in the coupling coefficients. The resulting Hamiltonian is solved variationally using a simple wave function. The results indicate that the Rashba spin-orbit interaction and the confining potential reduce the energy of the donor complex whereas the magnetic field enhances it. Interestingly enough, the binding energy is enhanced by the Dresselhaus spin-orbital interaction in the presence of a magnetic field and while it is reduced in the absence of it. Finally we study the effect of magnetic field and spin-orbit interactions on the magnetic moment and susceptibility.

The experimental study of the dynamic magnetic susceptibility of the powder of superparamagnetic nanoparticles of magnetite is presented. The powder has been obtained by removal (evaporation) of the liquid base of the magnetic colloidal solution (ferrofluid). The temperature dependences of the real and imaginary parts of the magnetic susceptibility at different frequencies of the measuring field have been obtained. The experimental findings are compared with the results of the simulations based on the numerical solution of the Landau-Lifshitz-Gilbert equation for the interacting superparamagnetic nanoparticles system. The conclusion has been made on the significant influence of the interparticle interactions on the magnetite superparamagnetic nanoparticles powder properties evidenced, in particular, by the decreased effective system relaxation time.

Present investigation deals with the exploration of magnetic susceptibility ( χ ) of doped GaAs quantum dot (QD) in a noisy ambience and following the variations of a few important physical quantities. The focus being to understand the interplay between noise and those physical quantities and how the interplay happens to modulate χ . Noise invoked here is of Gaussian white character and the impurity potential is also represented by a Gaussian function. The physical parameters involve magnetic field, confinement potential, dopant location, dopant potential, noise strength, aluminium concentration (in view of Al x Ga 1 - x As alloy QD), spatially-varying effective mass, spatially-varying dielectric screening function, anisotropy, hydrostatic pressure (HP) and temperature. The study also reveals the importance of the mode through which noise may enter the system. Whereas the additive mode of application of noise fails to affect χ noticeably from a noise-free state; the multiplicative mode of applying noise does the same quite conspicuously. Moreover, in general, whereas the system exhibits diamagnetism in absence of noise and under the supervision of additive noise; it is multiplicative noise which often induces paramagnetism in the system.

We have carried out detailed structural, magnetic and thermal properties studies of the Mn(Se, S) system. The detailed structural studies using synchrotron X-ray and neutron diffractions on MnSe confirm the coexistence of cubic and hexagonal phases at low temperature, which shows strong thermal hysteresis suggesting the first-order nature of the transition. Based on the temperature-dependent magnetic susceptibility, we confirmed that the substitution of the sulfur element to selenium critically modified the complex magnetism observed in MnSe. It was to our surprise to observe a magnetic anomaly at 16 K way below the antiferromagnetic order that sets at about 160 K in MnS. Our neutron study at low temperature did not reveal any additional magnetic structure below 16 K. However, the specific heat of MnS shows a clear T1.5 temperature dependence below 16 K, suggesting the possible emergence of a weak ferromagnetic order.

We find that the long range magnetic ordering is absent and electrical conduction suppressed in Y 1.7 Bi 0.3 Ir 2 O 7 /YSZ(1 0 0) thin film prepared by pulsed laser deposition. The sharp down-turn of inverse magnetic susceptibility χ - 1 ( T ) from the conventional Curie-Weiss behaviour below T ∗ ∼ 168 K suggests an inhomogeneous ferromagnetic Griffiths like phase. The transport and magnetic properties are explained on the basis of the coexistence of mixed oxidation states of Ir, (i.e. Ir 4 + and Ir 3 + ) leading to non-magnetic defects and reduction in t 2 g density of states at the Fermi level.

We study the problem of an electron, neutrally charged donor impurity ( D 0 ) and acceptor impurity in a two-dimensional (2D) semiconductor quantum dot (SQD) with parabolic potential in the presence of an external magnetic field within the effective-mass approximation by using the numerical matrix diagonalization method. The energy spectrum is calculated for an electron, donor impurity and acceptor impurity as a function of the magnetic field. We find the ground state (GS) magnetic moment ( μ gs ) and the GS magnetic susceptibility ( χ gs ) of an acceptor impurity system, It only shows zero temperature diamagnetic peaks, but an electron and the donor impurity does not. The position and the number of these zero temperature diamagnetic peaks depend on the strength of the confinement potential ( ω 0 ) . The binding energies of the few low-lying states are also obtained by directly calculating the energies of an electron and donor impurity and it shows that the donor impurity is stable in a parabolic quantum dot (PQD). The theory is applied to a GaAs PQD.

Magnetism at the nanoscale is intriguing, but that on the magnetic properties of a dilute antiferromagnetic (AFM) system is rarely studied. Presence of uncompensated spins at the lattice as well as on the nanoparticle surfaces could lead to interesting magnetic behaviour. We present the combined effect of reduction in particle size and dilution of exchange interactions on the magnetic properties of an AFM perovskite oxide. A dilute AFM compound, La2Fe0.875Cr0.125GaO6 nanoparticles (average particle size ∼ 44.5 (7) nm), has been synthesized where non-magnetic Ga-ions are introduced to interrupt the superexchange pathways. The compound crystallizes in orthorhombic structure with Pbnm space group, where Fe, Cr and Ga ions are distributed randomly in the B-site. DC magnetic studies show superparamagnetic behaviour at room temperature, spin-flop transition and a prominent hysteresis loop with sufficiently high coercivity around 6.69 kOe at ∼138 K. The analysis of thermoremanent and isothermoremanent magnetization curves reveal SPM behaviour at 300 K and 2-dimensional dilute antiferromagnetic in field like nature at 5 K. AC magnetic susceptibility analysis confirms the presence of non-interacting clusters having SPM behaviour with blocking temperature ∼280 K. Furthermore, temperature variation of coercivity shows a Gaussian nature, mainly associated with competing Dzyaloshinskii-Moriya interactions between disordered B-site ions along with strong uncompensated surface spin effects.

Effects of disorder, frustration and low dimensional character occur in mixed magnetic Co1−xNixCl2·H2O, examined by dc magnetization and susceptibility measurements across the composition range. The pure components are quasi-one-dimensional antiferromagnets ordering at 15.0 K (Co) and 5.65 K (Ni), with susceptibility maxima at 16.2 and 8.4 K respectively; a spin glass transition also appears in the cobalt system near 8 K. In each compound weaker antiferromagnetic interchain exchange interactions supplement dominant ferromagnetic exchange along MCl2MCl2M… chemical and structural chains. High temperature magnetic susceptibilities are analyzed to yield Curie and Weiss constants in χM = C/(T − θ). Regular but not mean-field composition dependences appear for C and θ. The former is not linear and the latter displays a minimum near x = 0.30. Notable is a susceptibility maxima varying in location only weakly from x = 0.10 to x = 0.70, decreasing markedly only for higher x. Magnetization isotherms evolve regularly as x varies, with systematic composition dependences of a metamagnetic transition field and hysteresis through x = 0.70. A qualitative change in the isotherms occurs for x = 0.90, but substantial curvature still appears with smaller but definite hysteresis. A thermoremanent magnetization is seen in all mixtures, and is largest for the composition extremes. Thus, nonequilibrium magnetic behavior characteristic of the cobalt component, in contrast to the more conventional nickel component, occurs even when the latter is present in strong majority.

International audience; A model of structured Magneto-rheological Elastomer made of a soft matrix filled by magnetic particles was studied for energy harvesting, in pure shear condition. The particles were supposed to be aligned in a chain along which the magnetic field is applied and considering a shear strain applied in a plane perpendicularly to the chain. As the strain is applied and assuming the deformation is homogeneous and the particles remain aligned, both of the axis of their alignment and inter-distance between particles change, affecting their magnetic state. The aim of this work is to evaluate how far the magnetic induction variation induced by mechanical solicitation can be converted into electric signal. We firstly analyzed the magnetic susceptibility of a particle in the chain, and then derived an analytical expression for the composite permeability as a function of shear strain. FEM simulations taking into account the particle magnetic saturation was also performed to estimate the optimal conditions (magnetic field values, shear amplitude, etc.) maximizing the energy conversion potentials.

Magnetic transitional behaviors and magnetocaloric effect of the intermetallic compound Ho3Pd2 have been studied. It exhibits a second order magnetic transition from ferromagnetic (FM) to paramagnetic (PM) states at a Curie temperature (TC) of 9.6 K. In the PM region, the magnetic susceptibility of the Ho3Pd2 compound follows the Curie-Weiss law. The paramagnetic Curie temperature (θp) was evaluated to be 5.3 K, and the effective magnetic moment (μeff) to be 10.5 μB/Ho. The positive value of θp indicates the ferromagnetic interactions in the ordering state of Ho3Pd2 and the effective magnetic moment is close to the theoretical value 10.6 μB for the Ho3+ ion, which suggests that the Pd ions in Ho3Pd2 are non-magnetic. Under the magnetic field change of 0–5 T, the maximum magnetic entropy change (−ΔSM) and the refrigerant capacity (RC) for this compound are evaluated to be 18.3 J kg−1 K−1 and 301.5 J kg−1, respectively, with no thermal and field hysteresis loss.

In this paper, we investigate the magnetic properties of the spin Lieb nanolattice for three sublattice with spins S = 1/2, σ = 3/2 and q = 1, in the presence of sites dilution. Furthermore, in order to study the effect of disorder, the spins S and/or q are diluted, while the spin σ stays pure. The work is carried out according to the Monte Carlo Simulations. We start this research by giving the total and partial magnetizations, then we present magnetic susceptibilities of the studied system. In addition, the variation of the magnetization with temperature of mixed spins ( s , σ and q ) with dilution is presented. The total magnetization with crystal and external fields and with dilution of mixed spins is obtained. Besides, we have presented the magnetic hysteresis cycles of spin Lieb structure, for different values of crystal-field and temperature and for different dilution values. To the best of our knowledge, no single research has been reported in the study of the dilution effect on the magnetic properties in the studied system.

The nanoparticles of the ZnxFe3−xO4 (0 ≤ x ≤ 0.5) ferrites have been synthesized using a simple co-precipitation method under air atmosphere at room temperature. The Fourier transform infrared spectroscopy and X-ray diffraction patterns confirm the formation of spinel mono-phase structure in all the samples. The results show that the crystallite size relates to the cationic distribution. The cation distribution is derived from the X-ray diffraction patterns enabling determination of ion coordination, ion occupancy and unit cell parameter. The magnetic hysteresis loops reveal that the magnetization increases with Zn content up to x = 0.3 and then decreases with further Zn doping, which is explained in terms of the competition between the influence of crystallite size and cations distribution (site occupancies). The thermal behavior of magnetization for the selected x = 0.3 sample is described by a modified Bloch law, based on the spin wave excitations in the particle core. Furthermore, the temperature of the AC magnetic susceptibility peak increases up to 0.3 Zn, then decreases by further Zn doping. The frequency dependence of AC magnetic susceptibility indicates the presence of strong interparticle interactions resulting in a superspin glassy state. The experimental evidence of memory effect in x = 0.3 sample further confirms the frustrated magnetic state in the compounds. The potential application of these materials for hyperthermia based therapy has been estimated. The results show that in the studied series, Zn0.3Fe2.7O4 with highest loss power is the best candidate for this therapy.

In single crystals of the solid solution Cs2 CuCl 4 - x Br x ( 0 ⩽ x ⩽ 4 ), depending on the growth conditions, two structural modifications with a tetrahedral or an octahedral Cu environment can be realized. The border compounds (x = 0 and 4) with a tetrahedral Cu coordination have been recognized as model systems for quasi-2D frustrated anisotropic triangular quantum antiferromagnets. This holds true also for the newly discovered stoichiometric compounds with x = 1 and 2. In contrast, the systems exhibiting an octahedral Cu environment can be classified as quasi-2D ferromagnets characterized by ferromagnetic layers with a weak inter-layer coupling. Here we study the magnetic and magneto-elastic couplings for the low-dimensional Heisenberg quantum magnet Cs2CuCl2Br2 with octahedral Cu coordination. By applying magnetic susceptibility measurements under varying hydrostatic (He-gas) pressure, χ ( T , p ) , we determine the pressure dependence of the magnetic coupling constant ∂ J / ∂ p and estimate the magneto-elastic couplings ∂ J / ∂ ∊ v . These values are enhanced by almost one order of magnitude compared to Cs2CuCl2Br2 with tetrahedral Cu coordination.

We present results from a study on the influence of the preparation technique on the structural and magnetic properties of Ba 0.5 Sr 1.5 Zn 2 Fe 12 O 22 powders synthesized by citric-acid sol-gel auto-combustion and sonochemistry and characterized by X-ray diffraction, scanning electron microscopy and magnetic measurements. Two magnetic intermediate phases were observed at room temperature in magnetic fields of moderate strength. Metamagnetic phase transitions were observed in an ac magnetic field. Their temperature increased with the magnetic field amplitude.

An alternate method of measuring anisotropy fields in thin film ferromagnets is demonstrated. The method relies on the magnetic susceptibility in a small a.c. magnetic field, measured \txtit{in situ} using the magneto-optic Kerr effect (MOKE), and will be useful in situations where more specialized apparatus are not available, or constraints discourage the use of a large, static magnetic field. The method is demonstrated for Co/W(110) films, where it yields anisotropy fields in agreement with previous studies using more conventional torque magnetometry. The sensitivity of the method is demonstrated using CoO/Co/W(110) bilayer films, where the anisotropy due to interfacial exchange coupling is detected and used to find the N\'{e}el temperature of the thin CoO layer., Comment: 8 pages, 5 figures

We report changes on the magnetic behavior of the Heavy-Fermion ferromagnetic YbNi 2 alloy when reducing the size of the particles to the nanometer scale by high-energy ball milling. The milling process induces a reduction on the particle size of the bulk alloy down to 10 (2) nm and a lattice strain of 1.8 (2)%, for 30 h of milling time, as calculated from the X-ray diffraction data. The ferromagnetic transition at T C = 10.5 K in the bulk alloy tends to disappear whereas other magnetic transitions arise at lower temperatures with the milling process. The AC magnetic susceptibility of the 30 h milled sample shows a frequency independent peak at 3 K, in a wide range of frequencies, consistent neither with superparamagnetic nor simple freezing of the magnetic moments, and as expected for a ferromagnetic behavior. However, from the specific heat measurements in the 30 h milled sample, a peak at 3.6 K is shifted respect to that observed in the AC magnetic susceptibility, as found in spin glasses. Additionally, the specific heat on nanometric samples show reduced magnetic contributions respect to the bulk alloy with Δ c max around 0.45 J/molK. The results are explained by the influence of magnetic inhomogeneities and disorder of the alloys enhanced by the milling process in the ensemble of nanoparticles.

The Griffiths phase in fine grain manganite La0.75Ca0.25MnO3 is studied by the complementary structural methods, DC magnetic susceptibility and ESR spectroscopy. The Griffiths like phase is detected above Curie temperature between 232 and 280 K and sustains up to high magnetic field of 3000 Oe. The magnetic susceptibility of Griffiths phase is a decreasing function of temperature. The magnetic field dependence of Griffiths phase susceptibility reveals its remarkable contribution to measured total susceptibility. The additional anomalous ESR signal supperimpossed on the paramagnetic one is ascribed to the locally inhomogeneous Griffiths like phase in agreement with the core – shell model.

Anomalous properties both of the dynamic magnetic susceptibility and the spontaneous magnetization of Y 3 - x Fe 5 + x O 12 garnet films have been experimentally observed. The most significant anomalies are the following: (a) an orientational magnetic transition at room temperature in the range of the applied magnetic field of 300–700 Oe; (b) a spontaneous magnetization vector reversal in the temperature range of 110–275 °C and the corresponding jump of the dynamic susceptibility at zero magnetic field; (c) oscillations of the magnetization in the paramagnetic state of the sample and the corresponding jumps of the dynamic susceptibility at the planar magnetic field H = 200 Oe. It has been established that all reported anomalies exhibit an inverse behavior, namely, with decrease of the applied magnetic field (or temperature) a reverse hysteresis of the field (or temperature) dependences both of the dynamic magnetic susceptibility and the spontaneous magnetization is observed. Possible reasons for such a behavior of the measured dependences are also discussed.

The effects of Gd3+ ion doping on the lattice structure and magnetism properties of polycrystalline SmFeO3 were investigated by X-ray diffraction (XRD) and magnetic characterization. Both the magnetic susceptibility and saturation magnetization were significantly enhanced due to the larger spin number of Gd3+. The low doping sample of Sm0.95Gd0.05FeO3 showed great enhancement of magnetic energy product, which may be attributed to the local exchange of different grains.

In this work, polycrystalline NiCrGa half Heusler alloy, which is predicted to be half-metallic ferromagnet from first principles calculations, has been synthesized by arc meting technique and its structural, magnetic as well as the electronic properties have been studied. The measured x-ray diffraction (XRD) pattern shows the signature of a disordered structure. From the magnetization measurements, there is no evidence of ferromagnetic ordering observed in this system down to the lowest temperature studied. Instead, the system shows the signature of an antiferromagnetic ordering at very low temperature. The experimentally observed structural and magnetic properties are found to be significantly different from the theoretically predicted properties of the ordered cubic C1b structure. To probe the possible disorder present in the system and its effect on the magnetic properties, we have carried out first principles calculations using the spin-polarized-relativistic Korringa-Kohn-Rostoker method (SPR-KKR). Using a combination of XRD, photoelectron spectroscopy, magnetization measurements and first principles calculations, we conclude that NiCrGa has significant amount of atomic disorder. Although, the ordered structure is energetically more stable than the disordered structures, we find that after synthesis, the system tends to stabilize in a disordered structure. With this atomic disorder present in the sample, the ferromagnetic ordering is disturbed and the calculated spin polarization is consequently reduced., Comment: 18 pages, 5 figures, 3 tables

Paramagnetic constituents of a cell have strong effect on cell’s volume magnetic susceptibility even at low volume fraction because of their high susceptibility relative to that of the diamagnetic cell constituents. The effect can be measured at a single cell level by measuring cell terminal velocity in viscous media using a microscope equipped with a well-defined field and gradient magnet configuration (referred to as magnetophoretic analysis by cell tracking velocimetry, CTV). The sensitivity of such a microscopic-scale magnetometry was compared to that of a reference method of superconducting quantum interference-magnetic properties measurement system (SQUID-MPMS) using a red blood cell (RBC) suspension model. The RBC hemoglobin oxygen saturation determines the hemoglobin molecular magnetic susceptibility (diamagnetic when fully oxygenated, paramagnetic when fully deoxygenated or converted to methemoglobin). The SQUID-MPMS measurements were performed on an average of 5,000 RBCs in 20 μL physiological phosphate buffer at room temperature, those by CTV on a single cell track in a mean magnetic field of 1.6 T and mean gradient of 240 T/m, repeated for an average of 1,000 tracks per sample. This suggests 5,000× higher sensitivity of cell susceptometry by magnetophoretic analysis than by SQUID-MPMS. The magnetophoretic mean RBC magnetic susceptibilities were in the range determined by SQUID-MPMS (lower limit) and theory (upper limit). The ability of magnetophoretic analysis to resolve susceptibility peaks in a mixed cell populations was confirmed for an oxy RBC and met RBC mixture. Magnetophoretic analysis by CTV provides new tool for studies of emergence of paramagnetic reaction products in the cell.

We study the magnon-charged impurity interaction effects on the magnonic heat capacity (MHC) and the Pauli magnetic susceptibility (PMS) of spin-1/2 and spin-3/2 Lieb lattice within the J 1 - J 2 Heisenberg model in the presence of the Dzyaloshinskii-Moriya interaction (DMI) and the Zeeman magnetic field. In so doing, we use the Green’s function technique and the full self-consistent Born approximation. We found that in the case of J 1 Heisenberg model, the MHC and PMS increase (decrease) with impurity concentration for spin-1/2 (spin-3/2), while oscillate (decrease) when coupling constants next-nearest-neighbor (NNN), DMI, and the Zeeman field are taken into account. We have also investigated perturbed MHC and PMS by ascertained impurity for different coupling strengths, resulting in the oscillating (decreasing) behavior with NNN for spin-1/2 (spin-3/2) and a decreasing behavior with DMI and Zeeman magnetic field for both spin-1/2 and spin-3/2. Moreover, magnetic phase transitions in the case of spin-3/2 are established when tuning coupling constants on the non-zero, whilst no magnetic phase transition is observed for spin-1/2 Lieb lattice. Our findings are useful to tune the physical properties of optical lattices subjected to the electric field, magnetic field, and charged impurity.

The thermodynamic Bethe ansatz equations of the Coqblin-Schrieffer model have been solved numerically. The full N=6 (J=5/2) degeneracy of the Hund's rule ionic ground state of Ce is taken into account. Results for the temperature dependent magnetic susceptibility parallel and perpendicular to the crystal axis are presented. The deviations, due to the Kondo effect, to the non-interacting ion results are pointed out., 4 pages, 2 figures, accepted for publication in Journal of Magnetism and Magnetic Materials

The magnetization of a magnetoactive elastomer (MAE) with microparticles of soft magnetic carbonyl iron embedded in a highly elastic matrix has been studied. It is shown that at high temperatures its magnetization curve has the form of a specific hysteresis loop. This hysteresis is attributed to the influence of displacement of magnetized particles in the elastically soft elastomer matrix under the effect of magnetic forces, leading to the change of magnetic interaction between the particles. In this case, there is a maximum in the field dependence of the magnetic susceptibility, the occurrence of which has been associated with the competition between re-arrangement of particles, when they are displaced in a magnetic field, and saturation of particles’ magnetization. When the MAE is cooled below approximately 225 K, both the magnetic hysteresis and the maximum in the field dependence of the magnetic susceptibility disappear. When the MAE material is cooled below the solidification temperature of the elastomer matrix, the displacements of the magnetic particles during magnetization are blocked by the rigid matrix. The magnetization reversal of the MAE is reversible. This means that the shape of subsequent magnetization loops remains constant and the sample returns into the initial non-magnetized state after the magnetic field is turned off.

In order to study the magnetic properties of a mixed spin 1/2 Ising model and spin 1 Blume-Capel model in a hexagonal nanotube two layers system, we carried out a Monte Carlo simulation with the Metropolis algorithm. By means of the magnetic susceptibility curves, the phase diagram for a finite size lattice is obtained. In association with previous analytic results, an uncommon increase in the magnetization with temperature is described by the existence of an unstable state with a non-zero order parameter.

Polycrystalline Sm1−xLaxFeO3 (SLFO, x = 0, 0.05, 0.1 and 0.2) samples were prepared by solid state reaction method. The effects of La ions doping on the structure and magnetic properties of SLFO samples were studied by X-ray diffraction (XRD) and magnetic characterization (magnetic hysteresis loops and temperature-dependent magnetic susceptibility). La ions could be successfully doped into SLFO up to 20% without phase transformation. By diluting the magnetic Sm ions with this non-magnetic La ions, the magnetic anisotropy energy of SLFO increased first and then followed by dropping, so the exchange bias (EB) field also increased first and then dropped. Temperature induced spin switching can be observed after zero field cooling procedure.

The problem of two interacting electrons moving in a two-dimensional semiconductor quantum dot with Gaussian confining potential under the influence of an external magnetic field is studied by numerical diagonalization of the Hamiltonian matrix. The energy spectrum, the magnetic moment and the susceptibility are calculated as a function of the magnetic field and the quantum dot parameters. The magnetic moment and the magnetic susceptibility are shown to have zero-temperature diamagnetic peaks due to the exchange-induced singlet-triplet oscillations. The position and the number of these peaks depend on the size of the quantum dot and also the strength of the electron-electron interaction. The addition energies of the two low-lying states are also obtained by directly calculating the chemical potential. Besides, the electric capacitance is calculated as well. The theory is applied to a GaAs quantum dot.

Co2W-type hexaferrite nanoparticles with composition of SrCo2−x(MnZnCa)x/3Fe16O27(x = 0–0.5) were synthesized by a co-precipitation method. The synthesized nanoparticles were decorated on the outer surface of multi-walled carbon nanotubes by chemical method. X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry, magnetic susceptometer and vector network analyzer were utilized to characterize the structural, magnetic, and reflection loss properties of the nanocomposites. The structural results showed a perfect diffusion of Mn, Zn and Ca ions into the crystal structure of Co2W hexaferrite without forming any secondary phases. The SEM images provide clear information about the size of nanoparticles (50–85 nm) through these samples. The hysteresis loops showed hard magnetic property with enhanced coercivity which reflects that the synthesized particles have almost high magnetic anisotropic field, well suitable for absorbing materials. The coercivity (Hc) increased from 1450 Oe at x = 0.0, to 1650 Oe at x = 0.3, and then decreases to 1320 Oe at x = 0.5. High reduction in the coercivity was detected consistent with the large particle sizes for these samples. Ferrite nanoparticles were decorated on the surface of carbon nanotubes in almost constant distance. The interacting mode was confirmed between magnetic nanoparticles by means of plotting real and imaginary parts of magnetic susceptibility versus temperature at various frequencies. Based on reflectivity measurement, the sample with x = 0.3 showed a maximum reflection loss of −37 dB at the frequency of 9.4 GHz. This sample revealed the best performance with low reflectivity and high absorption broadband (4 GHz) at X-band frequency range.

The experimental data are presented for magnetic susceptibility and electrical conductivity in PrBaCo 2 O 6– δ at 850–1223 K. The decrease of oxygen content at heating is accompanied by formation of Co 3+ cations that may simultaneously reside in oxygen pyramidal and octahedral coordination with intermediate and high spins, respectively. The small polaron p -type electron transport is shown to be mediated by the intermediate-spin Co 3+ while high-spin Co 3+ cations in octahedral environment are excluded from polaron jumps due to the spin blockade effect.

Magnetic dilution and NEXAFS spectroscopy were used in the study of iron-containing solid solutions Bi2MNb2O9 (M – Ba, Sr) with layered perovskite-like structure. The analysis of the NEXAFS Fe2p-spectra of iron-containing solid solutions and iron oxides revealed that the studied Fe atoms were mainly in the +3 oxidation state. The study of magnetic susceptibility of the Bi2Ba(Sr)Nb2−2xFe2xO9−δ solid solutions showed the influence of atoms of the second coordination sphere on the distribution, degree of clustering, and intensity of exchange interactions in clusters of iron atoms. It was established that iron (III) atoms exhibited selectivity in filling the cation positions, preferring less distorted octahedral positions. The substitution of barium with strontium atoms led to intensification of the exchange of the ferromagnetic type and to a decrease in the degree of clustering of iron atoms in the solid solutions Bi2SrNb2−2xFe2xO9−δ.

A tetranuclear iron grid-type spin crossover complex, [FeII4(HL)4](BF4)4·6H2O (1) (H2L = 2-(4-hydroxyphenyl)-4,5-bis{6-(3,5-dimethylpyrazol-1-yl)pyrid-2- yl}-1H-imidazole), was synthesized. Magnetic susceptibility measurements revealed that 1 shows gradual spin crossover behavior above 200 K. The electronic states of the compound were elucidated by Mossbauer spectra.

A constant rise in magnetic permeability with a simultaneous decrease in saturation magnetization, and Curie temperature has been recorded throughout the cobalt concentration studied in Ni-Zn ferrite system of composition, Ni0.57−yCoyZn0.35Mg0.08Fe2O4 (x = 0.00, 0.04, 0.08, 0.12, 0.16, 0.20). The observed increase in magnetic permeability with cobalt addition has been an unusual phenomenon in nickel zinc ferrites. The anomalous increase along with allied magnetic properties has been discussed in terms of the super exchange interactions between the cations occupying tetrahedral and octahedral sites and their distribution by studying lattice parameter, grain size and differential magnetic susceptibility.

Structural and magnetic properties of ZnFe 2 O 4 nanograins, prepared by high-energy ball milling and annealed, were systematically studied by X-ray diffraction, 57 Fe Mossbauer spectroscopy and AC magnetic susceptibility measurements. Disordered spinel-like structure, with a grain size of 12 nm, is established after 200 h of milling. While the 300 K Mossbauer spectrum of the as-milled sample (200 h) displays broad magnetic absorption lines, characteristic of a disordered system, the magnetization data do not show a magnetic phase transition between 4 and 300 K. At low temperatures, the Mossbauer spectra suggest the presence of two distinct ferrite magnetic phases: one attributed to the grain core (crystalline-like phase), with magnetic ordering temperature of about 90 K, and one showing a magnetic hyperfine field distribution; the latter is associated with a chemically disordered phase (grain boundary contributions). Annealing the 200 h sample at 973 K leads to an improvement of atomic ordering of the spinel structure (reduction of cationic inversion) and average grain size of about 17 nm. AC magnetic susceptibility shows a cusp at about T ≈ 30 K , whilst Mossbauer experiments in the same sample reveal magnetic blocking in the same temperature range. The frequency dependence of susceptibility suggests the formation of a cluster-glass-like state. High temperature susceptibility can be described with a Fulcher law of interacting magnetic clusters.

We report on the magnetic properties of geometrically frustrated K3CrO4, in which Cr5+ cations are arranged on a distorted pyrochlore lattice. The crystal structure, static and dynamic magnetic properties of the compound are investigated in detail. A combination of DC and AC magnetic susceptibility measurements together with thermoremanent magnetization decay measurements reveal several magnetic transitions: the onset of glassy canted antiferromagnetic order occurs at 36 K, followed by the appearance of ferromagnetic/ferrimagnetic cluster glass behavior below the freezing temperature of 20 K. Further field-induced, temperature-dependent transitions are observed in the range 3-10 K. The frequency dependence of the freezing temperature for the cluster glass state is analyzed on the basis of dynamic scaling laws including the critical slowing down formula and the Vogel-Fulcher law., A high-resolution version with supplementary material can be found at https://www.sciencedirect.com/science/article/pii/S0304885321004893?via%3Dihub. arXiv admin note: text overlap with arXiv:1912.05997

Specific heat, magnetic susceptibility and magnetization of Cu(en)2SO4 single crystal were investigated in the field applied along the b-axis. The analysis of the susceptibility within the Curie-Weiss law indicates the antiferromagnetic nature of the exchange coupling between Cu(II) ions with zJ/kB = −6.4 K. Considering the structure of this material, the formation of magnetic dimers can be expected. Very good description of susceptibility data was achieved using the Heisenberg antiferromagnetic dimer model with intra-dimer coupling J / k B = −5.52 K, effective inter-dimer coupling J ' / k B = −0.3 K and gb = 2.12. The energy gap in the spin excitation spectrum was estimated Δ/kB ≈ 11 K and corresponding critical field B c b ≈ 7.8 T required for closing the gap. The dimerized nature of magnetic interactions was also confirmed by specific heat and isothermal magnetization data which manifest qualitatively the same behavior as the aforementioned dimer model. The possibility of further low-temperature experiments in the closed gap regime is discussed to obtain more detailed concept of magnetic interactions in this interesting compound.

The temperature dependence of magnetic susceptibility, χ(T), of the (Cr84Re16)100−xVx alloy system is reported in this contribution. Anomalies are observed at the Neel temperature (TN), associated with the onset of the antiferromagnetic (AF) spin-density-wave (SDW) state, with these anomalies becoming more pronounced as x increases. The TN values determined from χ(T) measurements are in close agreement with that obtained from the measurement of temperature dependence of electrical resistivity, ρ(T). Prominent broad deep minima are observed in χ(T) upon cooling below 100 K which are followed by low temperature peaks in x = 10.4, 10.9 and 12.4 samples. A second anomaly, not associated with TN, is observed at a temperature TO TN.

Frequency and magnetic field dependences of the dynamic AC susceptibility of nanocomposites based on opal matrixes with Co and Pd particles have been experimentally investigated in the temperature range from 1.8 to 300 K at several frequencies of alternating magnetic field. Comparative analysis of the magnetic field dependences of the differential DC and dynamic AC susceptibilities has been carried out. The hysteresis loops of the nanocomposite samples were measured, as well as their structure and phase composition were studied. The magnetic field dependences of the differential DC susceptibility have been found to be close to the field dependences of the dynamic AC susceptibility measured at the frequency of 1 Hz but substantially differ from the susceptibility measured at the frequency of 10 Hz and higher. This fact indicates that long relaxation times exceeding ∼1 s are characteristic of the substance (Co+Pd). The frequency dependences of the dynamic AC susceptibility were used to calculate the relaxation times with the Cole-Cole formula. The sample with hexagonal Co and metallic Pd has been found to have three relaxation times of about 10-3, 10-2 and 1 s. At that, the field dependences of the differential DC susceptibility differ from the field dependences of the dynamic AC susceptibility measured at the frequencies of 10, 100 Hz and 1 kHz, which, in turn, are close to each other. This means that the eddy current losses are small in comparison with the magnetization reversal losses.

[Cu II (enpnen)]2[Mo IV (CN)8] ⋅ 7H2O (enpnen = N,N ′ - bis(2- aminoethyl)- 1,3 - propane- diamine) molecular cluster compound (1) was subject to a series of irradiations with the light of 405 nm. On irradiation isothermal magnetization at 1.8 and 5 K in the field range 0–70 kOe as well as magnetic susceptibility in the temperature range of 2–300 K were subsequently detected. Both types of magnetic signals were next analyzed assuming that the irradiation triggers two independent processes: the metal to metal charge transfer (MMCT) leading to a state with the Arrhenius-type relaxation and the spin crossover (SC) transition ending in a state whose relaxation displays a threshold behavior. The first mechanism leads to an electron from the spinless Mo(IV) configuration being transferred to one of the Cu(II) ions transforming the trimer into the state Cu(II)-N-C-Mo(V)-C-N-Cu(I), with spin 1/2 on the Mo(V) ion and the spinless Cu(I) ion. The other mechanism gives rise to an excited paramagnetic Mo(IV) ∗ linked to two paramagnetic Cu(II) centers with a possible superexchange interaction. The spin of the excited Mo(IV) ∗ species is equal to 1 and associated to a disruption of the 5s-electronic pair. A reasonable result of simultaneous fitting the full series of susceptibility and magnetization data to the model taking into account both mechanisms corroborates their presence.

Solid solutions (SS) based on Sr2MnSbO6 and SrLaMnSbO6 with mixed oxidation states of Mn have been prepared by solid state synthesis under standard conditions. The structural and magnetic properties of Sr2-xLaxMnSbO6 and Sr1.5La0.5Mn1+ySb1-yO6 have been studied using X-ray diffraction data and magnetic susceptibility χ and magnetization σ measurements at 2–400 K. The samples of the first group crystallize in the monoclinic space group P21/n, their unit cell volume increases with × due to the formation of mixed Mn3+/Mn2+ valence. The change of the Weiss constant Θ sign from positive to negative with variation of ×, as well as the divergence between FC and ZFC dependences χ(T) below 40 K and spin-glass behavior indicate that the dominant exchange interactions between Mn3+ and Mn2+ cations in Sr2-xLaxMnSbO6 are of antiferromagnetic nature. The samples of the second group (at y = 0.25 and 0.50) were characterized as non-uniform, containing apparently two phases with a mixed Mn3+/Mn4+ state. The composition of the phases was established approximately by studying their structural and magnetic characteristics. The composition and crystal structure of the main phases are similar to those of the monoclinic samples described above. The secondary phases are identified as rhombohedral (space group R 3 ¯ c ) with ferromagnetic properties with TC of 304.2 K (y = 0.25) and 365 K (y = 0.50).

In order to break the contradictory requirements of the outer shell electronic structure for multiferroism in oxide perovskites, multiferroic fluorides were selected to be studied, in which the ferroelectricity and ferromagnetism may both come from the same magnetic ions. Pure phase Ba5Fe3F19−δ powders were prepared by solid state reaction. Energy dispersive X-ray spectroscopy results indicate the deficiency of Fe. The mixed valence states of Fe3+ and Fe2+ are confirmed by X-ray photoelectron spectroscopy. The observation of amplitude and phase hysteresis loops measured by piezoresponse force microscopy indicates the ferroelectricity in Ba5Fe3F19−δ. The temperature dependent magnetization curves show a continuous increase with decreasing temperature, without clear phase transition. However, the temperature dependent inverse magnetic susceptibility (χ) follows the Curie–Weiss law above 150 K with Curie–Weiss temperature of −55 K, suggesting predominantly antiferromagnetic interactions between the Fe ions. The χT decreases with the temperature decreasing from 300 K, indicating the onset of weak antiferromagnetic interaction from temperature above 300 K. No hysteresis loop was observed for the magnetic dependent magnetization curves down to 5 K, indicating the lacking of long-range ordering. A peak was observed in the temperature dependent dielectric constant and dielectric loss at around 257 K, which was strongly suppressed by the application of 5 T magnetic field. The observation of magnetocapacitance effect confirms the magnetoelectric coupling, which originates from the magnetic and structural coupling.

A general theory of the shape tensor is outlined, providing estimates of the shape or demagnetisation factors for either single or collections of magnetic particles. In the general case of multiple interacting magnetic particles, shape factors are insufficient to completely characterise the magnetic field. This paper provides approximate expressions for the shape factors for isolated magnetic cylinders, isolated blocks, and collections of spheres. The key assumption is that the stray field is approximately spatially constant over each magnetic particle, leading to a system of equations for the shape factors. These equations are linear for magnetic particles of very high susceptibility, and imply shape factors have non-local properties. Non-random particle alignment can lead to very small shape factors, and corresponding high susceptibility, while random particle alignments tend to produce shape factors approximating their isolated values. The special case, when the matrix system for the shape factors is singular, corresponds to the threshold when the composite susceptibility changes from depending on, to being independent of, the particle susceptibilities. An appendix summarises the magnetic fields from uniformly magnetised point dipoles, spheres, cylinders, ellipsoids and blocks.

We have studied the effect of Al doping on structural, magnetic and electrical properties of La 0.8 Ba 0.2 Mn 1 - x Al x O 3 ( 0 ⩽ x ⩽ 0.25 ) manganite annealed in 750° and 1350° temperatures. Results show T c decreases as Al ion substitution in Mn site. The magnetic susceptibility measurement shows Griffiths and spin-glass phase in aluminum-doped samples. Recently, Narreto et al., reported dynamic distortion and polaronic effects in the paramagnetic state of La 0.8 Ba 0.2 Mn 1 - x Al x O 3 manganites. Here we completed the phase diagram and show an occurrence of the spin-glass state in this manganite. The resistivity measurement shows, T MIT (metal-insulator) transition temperatures decreases and the system become an insulator. The insulator–metal transition occurs for the undoped sample annealed at the low temperature in near 165 K, while this transition is weak for the undoped sample annealed at high temperature due to oxygen non-stoichiometry. Using three models VIZ., Adiabatic small polaron hoping, Variable range hopping, and Percolation model, the resistivity have been studied.

An iron nanowire encapsulated in carbon nanotubes doped with copper (Fe@CuCNTs) can be described as anisotropic Ising model. General formulas of the magnetization and the magnetic susceptibility for the system are calculated based on the effective field theory with correlations (EFT). The effects of the exchange coupling, the anisotropy and the external magnetic field on the magnetic properties of the system have been discussed. The structure index N of armchair carbon nanotube plays an important role in magnetization, susceptibility, blocking temperature and hysteresis loop for the system. This system maybe has potential applications in information recording and spintronics.

Crystals of ludwigite Ni2.14Mn0.86BO5 were synthesized by flux growth technique. We show in the paper that it contains Mn3+ and Mn4+. A possible mechanism of the manganese valence states stabilization has been proposed. The structural and magnetic characterization of the synthesized samples has been carried out in detail. The cations composition and Mn valence states of the crystal were determined using X-ray diffraction and EXAFS technique. The comparative analysis was carried out between the studied crystal and Ni2MnBO5 synthesized previously. Magnetic susceptibility measurements were carried out. The magnetic transition in the studied composition occurs at the 100 K that is higher than in Ni2MnBO5 although the studied composition is more disordered. The calculations of the exchange integrals in the frameworks of indirect coupling model revealed strong antiferromagnetic interactions. The several magnetic subsystems existence hypothesis was supposed. The possible magnetic structure was suggested from the energies estimation for different ordering variants.

We have studied the enhancement of Kondo scattering in the heavy fermion compounds Ce 2 Ni 3 Ge 1 - x Si x 5 by measuring electrical resistivity ρ ( T ) , magnetic susceptibility χ ( T ) , isothermal magnetization M ( B ) , specific heat C P ( T ) and magnetoresistance. All the members of this series crystallize in U 2 Co 3 Si 5 -type orthorhombic structure with space group Ibam . Magnetic susceptibility and specific heat data show that two step antiferromagnetic transitions at x = 0 reduce to a single transition at x = 0.15 followed by a complete suppression of antiferromagnetic ordering at x = 0.20. Positive magnetoresistance below the transition temperature confirms that the transitions are antiferromagnetic up to x = 0.15 and the negative magnetoresistance in the paramagnetic region implies the freezing out of spin-flip scattering in Kondo compounds under the application of magnetic field. Kondo temperature, estimated from paramagnetic Curie temperature and magnetoresistance data, increases with increasing x in Ce 2 Ni 3 Ge 1 - x Si x 5 for x ⩽ 0.80 . The γ values also indicate that the Kondo temperature enhances with increasing x after the suppression of antiferromagnetic ordering. Maximum γ value ( ∼ 76 mJ mol −1 K −2 Ce −1 ) is observed at x = 0.20 which indicates that the heavy fermion behavior is more pronounced at the magnetic-nonmagnetic boundary. A significant resistivity increase at a particular magnetic field is observed for T = 3.5 K, 3.8 K and 4 K ( x = 0 sample) and it is observed for T = 3 K ( x = 0.15 sample).

A colloidal ferrofluid (FF) with superparamagnetic iron oxide nanoparticles (SPION) has been investigated for the AC breakdown strength during the accelerated thermal aging test. Three volume concentrations of a transformer oil based FF were subjected to the accelerated thermal tests at the temperature 90 °C. AC breakdown strength (BDS) tests were carried out every 200 h period for up to 600 h. The breakdown probabilities were calculated according Weibull distribution function. Measured BDS populations were compared with a base carrier oil. The BDS median of the clear carrier oil has been observed to fall down 1.54 times, however for particular FF samples it dropped 2.31, 2.90 and 3.63 times, respectively, when comparing properties of the samples before testing with the samples after aging. Final BDS probability distributions show that the dielectrics withstand voltage of FF became lower than that of the carrier oil. The long-term thermal load of the particular FF is critical for its colloidal stability, which is deduced to be the main reason of such a significant BDS reduction. The impact of the thermal aging on the AC magnetic susceptibility is briefly documented, too.

We report crystal growth, magnetic properties and electron spin resonance (ESR) study of the one dimensional zigzag-chain compound FeNbO4. The single crystals were grown by the flux method using Na2WO4·12H2O and Na2W2O7 as the flux. Magnetic susceptibility and specific heat data show an antiferromagnetic ordering below 44 K. High-field magnetization data reveal a spin-flop transition at 12 T when magnetic field is applied along the magnetic easy axis. Multi-frequency ESR study on the single crystals reveal three resonance modes which can be understood by the molecule-field theory. Using a simple model with easy-axis type anisotropy, we estimate that the anisotropy field HA and the exchange field HE are 2.67 T and 27 T, respectively. The zero-frequency resonance field at 11 T corresponds to the spin-flop transition, demonstrating a close correlation between the high-field magnetization and the ESR spectra.

Diluted bulk magnetic alloy semiconductors DyxGe1−x (x ≤ 0.02) were prepared by a two-step fabrication procedure and studied experimentally by XRD, EDX and magnetic methods. The polycrystalline materials had the ccp (cubic closed-packed) structure of the host Germanium up to ≈2 at.% of Dysprosium. They exhibited different low-temperature and high-temperature behavior. Low-field dc magnetic susceptibility data showed sharp peaks and irreversibility between zero-field cooled and field-cooled states for x