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We report the decoupling of Gd–Cr magnetism and the resulting giant magnetocaloric effect in honeycomb-lattice tellurate GdCrTeO6. This compound adopts the hexagonal structure with the space group P-3. The susceptibility curve presents a paramagnetic behavior from room temperature to 2 K. Very intriguingly, however, the heat capacity measurement probes a λ-like peak at TN = 10 K, characterizing the long-range antiferromagnetic order. This suggests that the Gd and Cr sublattices are magnetically independent, i.e., the Gd ions are paramagnetic and the strong paramagnetism nearly masks the antiferromagnetic order of Cr ions, which is further evidenced by our ESR data. The maximum magnetic entropy change at 2 K is 41.8 J kg−1 K−1 in a field range of 0–7 T and 30.3 J kg−1 K−1 for 0–3 T, larger than those of most of the Gd oxides reported. The observed giant magnetocaloric effect is due to strong paramagnetism of Gd ions. [ABSTRACT FROM AUTHOR]

Soy protein is one kind of environment‐friendly nonbioactive plant protein with excellent properties. Paramagnetic γ‐Fe2O3 nanoparticles with a mean particle size of 7 nm are prepared by submerged circulative impinging stream reactor (SCISR). And a series of soy protein isolate (SPI)/Fe2O3 nanocomposites with excellent magnetic performance have been successfully prepared with glycerol as plasticizer and γ‐Fe2O3 as fillers. The results show that the strong hydrogen bonds are formed between polar amino acids of SPI and the fillers. The Fe2O3 nanoparticles exhibit homogeneous dispersion in the protein matrix. The resulting SPI/Fe2O3 nanocomposites exhibit good paramagnetism and good microwave absorbing properties at 2–18 GHz. In addition, the mechanical properties and thermal stability of soy protein materials are improved with the addition of Fe2O3 nanocomposites. The interactions between the fillers and matrix as well as between the fillers would influence the reinforcing effect of Fe2O3. These natural resources based on green functional materials would exhibit wide potential applications in electromagnetic interference shielding and packaging areas. [ABSTRACT FROM AUTHOR]

Despite being difficult to identify, extremely dilute oxygen vacancies have been widely reported to play an important role in enhancing magnetism in ZnFe 2 O 4. The mechanisms underlying this enhanced magnetism have not been well understood for a long time and remain controversial because the formation of oxygen vacancy-rich ZnFe 2 O 4 can be accompanied by changes in the chemical/physical characteristics, especially the composition, particle size, surface morphology and cation distribution, which can significantly affect the magnetization. An open and important question is whether and to what extent the enhanced magnetization can be attributed only to oxygen vacancies. In this study, the relationship between the magnetization and oxygen vacancies in ZnFe 2 O 4 was definitively determined by using a carefully designed "shake-and-heat" treatment to prepare vacancy-rich samples while keeping the other crystal/surface parameters constant. Compared to the nearly vacancy-free paramagnetism samples, the vacancy-rich samples exhibited a higher magnetization of approximately 5 emu/g at both 300 K and 2 K. The Fe3+-O2--Fe3+ superexchange paths broken by oxygen vacancies then resulting in the Fe3+-Fe3+ ferromagnetism configuration. Meanwhile, the oxygen vacancy is highly diluted then the ferromagnetism configuration is confined in a single super-cell, favoring a short-range magnetic ordering at room temperature. The concentration of oxygen vacancies was calculated to be 0.68% by magnetization measurement. Our results may shed a light on how oxygen vacancies affect magnetism. [ABSTRACT FROM AUTHOR]

Bi 25 FeO 39 microcrystals were synthesized via a one-pot hydrothermal process without additives, where their hierarchical structures could be designed from tetrahedron to orchid and marigold by the increment of pH values and reaction time. For all types of as-prepared Bi 25 FeO 39 , a high crystallinity and purity was confirmed in XRD and XPS analysis. A good thermal stability up to 1000 °C was revealed by DSC-TG with two endothermal peaks corresponding to decompositing and melting. A magnetic transition between ferromagnetism and paramagnetism around 36.3 K was distinguished from thermomagnetic curves as well as hysteresis loops at 5 K and 300 K respectively. In contrast to tetrahedron and orchid shaped Bi 25 FeO 39 , marigold shaped Bi 25 FeO 39 exhibited a higher magnetization up to 4.8 emu/g at 5 K and enhanced photocurrent density around 0.37 μA/cm2. The special crystal arrays and increased concentration of Fe should be responsible for it. This work paves an attractive way for facile preparation and potential applications of sillenite materials. [ABSTRACT FROM AUTHOR]

Interaction of the trilacunary 9-tungstosilicate [A-α-SiW9O34]10− with cobalt(II), nickel(II) and zinc(II) ions in pH 9 aqueous medium at room temperature led to the formation of the respective M4-containing heteropolytungstates [M4(OH)3(H2O)2(α-SiW10O36.5)2]13− (M = Co2+ (1), Ni2+ (2), and Zn2+ (3)). Polyanions 1–3 were characterized in the solid state by single-crystal XRD, FT-IR spectroscopy, and thermogravimetric and elemental analyses. Electrochemical studies showed that the Co2+ ions in 1 can be oxidized to Co3+ and the CVs of the WVI centers of the polyanions feature well-defined and chemically reversible reduction waves. Magnetic measurements on 1 and 2 showed paramagnetism with complex ferromagnetic and antiferromagnetic interactions. A model was presented for extracting the exchange constants for the magnetic exchange interaction. [ABSTRACT FROM AUTHOR]

Magnetoacoustic concentration tomography of magnetic nanoparticles (MNPs) with magnetic induction (MACT-MI) is a method that has been propsed recently for MNP concentration tomography for use in targeted therapy. This procedure has the advantages of being noninvasive, having high-resolution and providing quantitative estimation of MNPs. In order to further fundamentally increase the signal-to-noise ratio of the magnetoacoustic signal, the forward problem of MACT-MI in the saturation magnetization state was studied, especially the magnetization characteristics of MNPs, including the derivation of the force formula of MNPs in the saturation magnetization state and the relationships among the gradient of the external magnetic field, magnetic force, number concentration and sound pressure. Firstly, the magnetic force formula of MNPs in the saturation magnetization state was derived according to the classical Langevin theory of paramagnetism. Then, a 2D model was constructed to calculate the magnetic flux density, magnetic force and sound pressure. Finally, the 2D distribution diagram of magnetic force and sound pressure and its corresponding 1D curve were obtained. The simulation results showed that the saturation magnetic field produced by the Maxwell–Helmholtz coils made the MNPs magnetically saturated. Compared with the MNPs in an unsaturated magnetization state, the magnetic force of MNPs in the saturation magnetization state was stronger, and the stronger magnetic force could generate stronger magnetoacoustic signals, which made it possible to measure magnetoacoustic signals with higher signal-to-noise ratio. The research results can provide a research basis for the design of equipment for further MACT-MI experiment and clinical application. [ABSTRACT FROM AUTHOR]

Pure semi-ionic F-doped graphene with the s-F concentration high up to 17.4 at.% (s-FG-17.4) and covalent F-doped graphene with the c-F concentration of 17.8 at.% (c-FG-17.8) were synthesized by fluorination of graphene respectively at the low temperature of 100 °C and the conventional temperature of 200 °C. The electronic and magnetic properties of the two samples were studied. The results show that s-FG-17.4 is metal and exhibits strong ferromagnetism with the Curie temperature of 229 K and high magnetization of 1.1 emu/g; by contrast, c-FG-17.8 is semiconductor and exhibits spin-half paramagnetism with low magnetization of 0.1 emu/g. Thus, this study provided a reliable method to synthesize high-concentration pure s-FG and proposed an effective sp 3 dopants for obtaining metallic and ferromagnetic graphene with high magnetization. [Display omitted] [ABSTRACT FROM AUTHOR]

This letter reports a demonstration of microwave assisted magnetization reversal (MAMR) in a CoFeB film and the damping dependence in MAMR through the measurement of ferromagnetic resonance (FMR). Spin-pumping in non-ferromagnetic/ferromagnetic films provides a large range variation of Gilbert damping constants in magnetic samples when changing the thickness of non-ferromagnetic layers without changing the ferromagnetic film. An evident dependence of switching fields on the damping constant is observed in the presence of microwaves. The trend of the experimental data is well reproduced by a numerical simulation based on the Landau-Lifshitz-Gilbert equation. The result indicates that the large damping decreases the efficiency of microwaves in reducing the magnetization switching field. [ABSTRACT FROM AUTHOR]

The nonlinear stationary ac response of the magnetization of assemblies consisting of (i) noninteracting uniaxial superparamagnetic nanoparticles with aligned easy axes and (ii) randomly oriented nanoparticles subjected to superimposed ac and dc bias magnetic fields of arbitrary strength and orientation is calculated by averaging Gilbert's equation augmented by a random field. The magnetization dynamics of uniaxial particles driven by a strong ac field applied at an angle to the easy axis of the particle (so that the axial symmetry is broken) alters drastically leading to new nonlinear effects due to coupling of the thermally activated magnetization reversal mode with the precessional modes via the driving ac field. In particular, the high frequency response reveals significant nonlinear effects in the precessional motion with significant consequences for the dynamic hysteresis and ultra-fast switching of the magnetization following an ultrafast change in the applied field. [ABSTRACT FROM AUTHOR]

The effect of multiple defects on the energy barrier of magnetization reversal in a one-dimensional magnetic nanowire is studied. By numerically solving the double Sine-Gordon equation via the finite-difference method, we obtain the energy saddle point through which the initial magnetic state jumps to the final ground states. The energy barrier which is defined as the difference between the energies of the saddle point and the initial states is calculated for various defect parameters. It is found that the energy barrier strongly depend on the number and distribution of the defects. For given defects, there exists an optimal distribution for a minimum energy barrier. [ABSTRACT FROM AUTHOR]

We have synthesized and study the magnetic properties of (Fe0.25Nd0.75)0.6B0.4 amorphous nanoparticles. These particles were prepared in dispersed (polymeric matrix) and powder systems in order to investigate both the internal magnetic order of the particles and the effects arising from the interactions among them. The results obtained for the dispersed particles evidence the presence of an internal magnetic structure of the particles with a magnetically ordered core plus a paramagnetic shell. At low temperature, the core magnetic moment interacts with the shell (intraparticle interaction) inducing an enhancement in the effective magnetic anisotropy of the particles, which is related to the sharp increase in the coercive field at low temperatures. The interparticle interactions affect mainly the surface spins and induce a decrease in the total magnetization of the particle. [ABSTRACT FROM AUTHOR]

Simultaneous high-Curie temperature (TC) ferromagnetism and enhanced temperature-independent paramagnetism (χTIP) is quantified in TiO2 anatase nanorods doped with nominal 0.5 at % Fe synthesized by a hydrothermal route. The nanorod dimensions are 8–35 nm in width and several hundred nanometers in length and possess an Fe concentration of 0.3–1.0 at %; no evidence of pure iron nanoparticles is detected. Magnetometry shows ferromagnetism at low fields that transitions to paramagnetism at higher fields with an enhanced temperature-independent susceptibility >100 times that of pure bulk anatase TiO2. The enhanced magnetism is tentatively attributed to the defect structure of the nanorods. [ABSTRACT FROM AUTHOR]

The electronic transport and magnetism in half-doped Nd0.50Ca0.25Sr0.25MnO3 manganites have been investigated. Contrary to general half-doped system, it only displays a paramagnetic-ferromagnetic phase transition associated with an insulator-metal transition instead of with any features of charge ordering. With the decrease of temperature, an electronic phase separation and spin glass state occur in low temperature. We suggest that the A-site cation disorder induced by the size mismatch between Sr2+ ion and Ca2+ ion is mainly responsible for this phenomenon. [ABSTRACT FROM AUTHOR]

Magnetization reversal phenomena (MRP) along magnetic order-order transitions have recently been reported on impurity-doped magnetic systems. Because imperfect long-range magnetic order exists in these systems, it is expected that a systematic investigation of MRP will give physical information on thermomagnetic processes of magnetic systems in the range from the micro- to nanoscales. As a typical order-order transition (a state doubly modulated by helical and canting orders to a collinear ferrimagnetic state) has been known to occur on Cr5S6 at a transition temperature Tt, we investigate the magnetizations of (Cr0.70Ti0.30)5S6 on heating and cooling runs in various magnetic fields. At 20 Oe, the field-cooled magnetization just below the Curie temperature has a positive sign; the sign turns negative below the compensation temperature TCM (first step) and finally returns to positive below Tt (second step). The first-step MRP observed in this system is explained by the potential barriers resulting from anisotropy energy when the preferred direction of collinear ferrimagnetic moment reverses. The proposed mechanism for second-step MRP is the pinning effect caused by the impurity atoms (Ti) in the helical long-range-order chains. Comparing other examples of MRPs, we discuss the roles of local impurity centers in the thermomagnetic process in magnetic order-order transitions. [ABSTRACT FROM AUTHOR]

We study the speed of the magnetization switching resulting from spin transfer in pillar-shaped CoFe/Cu/CoFe spin valves and the temperature dependence thereof. The switching speed was investigated with current pulses of durations from 100 ps to dc while the temperature was varied from 50 to 300 K. Quasistatic loops indicate that the reversal events imply transition states with reduced remanences. Their interval of occurrence shrinks gradually to almost null when the temperature is raised to 300 K. The curvature of resistance versus current hysteresis loops is different in the antiparallel and parallel branches, which evidences the influence of the Ampere field on the quasistatic micromagnetic configuration. In the dynamical regime, the pulse-induced parallel to antiparallel transition speed is not much temperature dependent from 50 to 300 K. In contrast, the pulse-induced antiparallel to parallel transition is thermally disfavored and much faster at 150 K than at 300 K. We model the experimental behavior by a competition between thermal fluctuations and the Ampere-field-related C-like bending of the magnetization in the free layer. The contribution of the Ampere field dominates in most cases. These contributions are amplified or damped together by the spin-transfer torque, but since the C-like bending is a response to a magnetic field, it sets in at a gradual pace ruled by the classical Gilbert relaxation. Most of the difference between quasistatic switching and pulse-induced switching results from this complete or incomplete alignment with the total effective field. Our demonstration of 100-ps switching validates spin-transfer switching for fast memory applications. [ABSTRACT FROM AUTHOR]

A detailed study on the influence of particle size varied from 8 nm to 53 nm on the structural and magnetic properties of La0.8Sr0.2MnO3 - δ a has been done. The unit cell volume increases and the microstrain in the compound shows peak formation as the particle size decreases. Nano particles of La0.8Sr0.2MnO3 - δ exhibit superparamagnetism whose blocking temperature has a nonlinear and logarithmic decreasing tendency as function of particle size and applied magnetic field, respectively. Evidence of formation of a magnetically dead layer at the surface has been found and the ratio of the thickness of the dead layer to the particle size increases exponentially with particle size. The coercivity of the nanoparicles increases manifold as particle size varies from 53 nm to 21 nm. In the single domain region the coercivity exhibits a d-1.125 behavior. The temperature dependence of the saturation magnetization shows strong collective excitation due to the spin wave that varies as Tα with α > αbulk of 3/2. Thus the spin wave does not follow the Bloch law in the case of nano particles of La0.8Sr0.2MnO3 - δ. [ABSTRACT FROM AUTHOR]

Low-temperature magnetic properties were investigated on the gold nano particles (GNPs) with an average size of 11.5 nm, assembled with molecules of ruthenium complex (Ru0), and phenylboronic acid (B0) by the proton nuclear magnetic resonance (1H-NMR) and susceptibility measurements. The temperature dependence of the NMR shift and the uniform susceptibility was described as the sum of the Curie–Weiss term and a positive constant term. From the former, the average number of Ru0 on each GNP was estimated to be 118, which is 23% of the calculation. The finite positive constant term shows a clear contrast with the well-known fact that the bulk gold is diamagnetic. Finally, a disappearance of the motional narrowing effect in the proton NMR spectra below 60 K indicates that the wavering motion of Ru0 complexes on GNP at room temperature is frozen at low temperatures. [ABSTRACT FROM AUTHOR]

Permanent magnet materials based on the MM 2 Fe 14 B (MM = Misch-metal) are widely noted. However, as a room temperature paramagnetic phase, the existence of CeFe 2 phase in MM 2 Fe 14 B alloy is unavoidable. In order to eliminate the CeFe 2 phase, the La substitution on MM in MM 2 Fe 14 B alloys was described. Alloys with nominal composition of (La x MM 1−x ) 33 Fe 66 B (x = 0, 0.025, 0.05, 0.075, 0.1, 0.15) were prepared, and the crystal structure and magnetization of the (La x MM 1−x ) 33 Fe 66 B alloys were investigated. XRD results reveal that the lattice parameter a, c, unit-cell volume V, and c/a ratio of (La x MM 1−x ) 33 Fe 66 B alloys increase linearly with the La increase, indicating that La atoms enter into the main phase. Key to this study is the finding that CeFe 2 phase disappears with the La content above 0.075. It is therefore concluded that La substitution could inhibit formation of CeFe 2 phase. This is consistent with the observation from SEM-EDS. Another interesting finding is that La substitution would cause the change of Nd, Pr, La and Ce ratio in main phase, which means the ratios of four rare earth elements change with the La substitution. With the increase of x, the (Pr + Nd)/(La + Ce) ratio in main phase of (La x MM 1−x ) 33 Fe 66 B alloys decreases first, showing the lowest point at x = 0.075, and then increases. As a result, the saturation magnetization (M s ) of (La x MM 1−x ) 33 Fe 66 B alloys has the same tendency, which decreases from 11.78 kG (x = 0) to 11.35 kG (x = 0.075) first, and then increases to 11.96 kG (x = 0.15). And the Curie temperature (T c ) displays the same trend compared to the M s . These facts show that the MM has a great potential to prepare the low cost sintered permanent magnets. [ABSTRACT FROM AUTHOR]

Using an efficient first-principles computational scheme, we calculate the intrinsic stacking fault energy ( γ i s f ) and the unstable stacking fault energy ( γ u s f ) of paramagnetic γ -Fe as a function of temperature. The formation energies are derived from free energies accounting for thermal longitudinal spin fluctuations (LSFs). LSFs are demonstrated to be important for the accurate description of the temperature-dependent magnetism, intrinsic and unstable stacking fault energies, and have a comparatively large effect on γ i s f of γ -Fe. Dominated by the magneto-volume coupling at thermal excitations, γ i s f of γ -Fe exhibits a positive correlation with temperature, while γ u s f declines with increasing temperature. The predicted stacking fault energy of γ -Fe is negative at static condition, crosses zero around 540 K, and reaches 71.0 mJ m −2  at 1373 K, which is in good agreement with the experimental value. According to the plasticity theory formulated in terms of the intrinsic and unstable stacking fault energies, twinning remains a possible deformation mode even at elevated temperatures. Both the large positive temperature slope of γ i s f and the predicted high-temperature twinning are observed in the case of austenitic stainless steels. [ABSTRACT FROM AUTHOR]

A series of paramagnetic ionic liquids (PILs) based on N , N ′-bis(alkyl)imidazolium bromotrichloroferrate(III), [(C n ) 2 Im][FeCl 3 Br] (Im = imidazole; C n  = ethyl, butyl, hexyl, octyl, decyl, dodecyl), was prepared and compared against the more traditional [C n C 1 Im][FeCl 3 Br] (C 1  = methyl) analogs. Both series were extensively characterized by physical, chemical, and computational methods including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), spectroscopy (FTIR and UV‐vis-NIR), magnetic susceptibility, surface tensiometry, density, and viscosity. The X-ray crystal structure of [(C 12 ) 2 Im][FeCl 3 Br] was also obtained. Notably, all ionic liquids prepared in this study show short-term thermal stabilities exceeding 300 °C in air and have melting points equal to or lower than 25 °C, which is surprisingly low for ionic liquids containing symmetrical cations. In addition, all presented ionic liquids have relatively low viscosities allowing for easier transitioning into applications. Physical property trends are discussed. [ABSTRACT FROM AUTHOR]

Focuses on a study which presented evidence that the magnetism in annealed samples is due to fine magnetic particles. Condition which superparamagnetism is observed; Tool for the study of kinetics of crystallization; Behavior that is closely related to the precipitation of a very fine metastable body-centered-cubic phase in a nonmagnetic matrix.

The bulk and local magnetisms of ∼10 nm diameter CoFe2O4 nanoparticles have been characterized from 5 to 425 K. Magnetometry results indicate that the nanoparticles have a blocking temperature around 380 K and they exhibit a temperature dependent cubic magnetocrystalline anisotropy similar to that of bulk CoFe2O4 with K(0)∼1.2×106 ergs/cm3. However, the local, atomic-level spin dynamics examined by Mössbauer spectroscopy indicates strongly that rather than exhibiting a typical static, blocked magnetism to superparamagnetism behavior, the CoFe2O4 nanoparticle moments become paramagnetic, with this transition percolating from the surface to the core of the nanoparticle with increasing temperature. [ABSTRACT FROM AUTHOR]

A dynamic model of the asymmetric Ising glass is presented: an Ising model with antiferromagnet bonds, -J, and ferromagnetic bonds, +J, with probabilities q and 1-q. The dynamics is introduced by changing the arrangement of the antiferromagnetic bonds after n Monte Carlo steps but keeping the same value of q and spin configuration. In the region where there is a second order transition between the ferromagnetic and paramagnetic states at Tc(q) for qq0 where there is a first order transition between the ferromagnetic and spin glass states where it shows no effects of motional narrowing. The implications of this are discussed. This model is devised to explain the properties of doped ZnO where the magnetization is reduced when the exchange interactions change with time. [ABSTRACT FROM AUTHOR]

Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn-Mn bonds, deciding between competing crystal structures. [ABSTRACT FROM AUTHOR]

One-pot reactions of pre-assigned molar ratios of appropriate metal (II) salts and HL 1 (2-acetylpyridine nicotinoylhydrazone) or HL 2 (2-acetylpyridine isonicotinoylhydrazone) in MeOH solutions at room temperature afford 1D coordination polymeric chain [Cu(μ-L 1 ) (Cl)] n ( 1 ) and a mononuclear complex [Ni(L 2 ) 2 ] ( 2 ). The compounds ( 1) and ( 2 ) were characterized using elemental analyses, spectral and other physicochemical methods. Single crystal X-ray diffraction measurements for ( 1 ) and ( 2 ) have been made to define the molecular aggregates and crystalline architectures. In ( 1 ), each copper (II) center adopts a distorted square pyramidal geometry with a CuN 3 OCl chromophore linked through μ-L 1 to form the 1D polymeric chain. While in ( 2 ) each Ni(II) cation is six-coordinate with octahedral structure having NiN 4 O 2 chromophore containing two L 2 units each functioning as a classical tridentate (N,N,O) chelator. Different weak non-covalent interactions promote dimensionalities in the compounds. A Hirshfeld surface analysis was employed to gain additional insight into interactions responsible for packing of ( 1 ) and ( 2 ). Magnetic susceptibility measurement of (1 ) in the 4–300 K range reveals simple paramagnetism. [ABSTRACT FROM AUTHOR]

In this work, a new intercalated FeS compound: (C 2 H 8 N 2 ) 0.4 Fe 2 S 2 was synthesized via the solvothermal route. The product is stable in air and shows the micron-sized plate shape. Structure refinement indicates that (C 2 H 8 N 2 ) 0.4 Fe 2 S 2 adopts the I 4/ m space group with the lattice constants a = 3.6906(6) and c = 20.4215(11) Å. The [FeS] layer crystallizes into the anti-fluorite structure with edge-sharing tetrahedrons and the C 2 H 8 N 2 molecules are inserted in between the layers. (C 2 H 8 N 2 ) 0.4 Fe 2 S 2 is the first intercalated FeS compound reported up to now that contains the electroneutral guest layers. This specific feature leads to the paramagnetic behavior without any magnetic transition in the measured temperature range. Furthermore, we find that the ferromagnetic interaction can also be easily induced in this compound by inserting the extra Fe in between the layers, indicating the controllable magnetism of the title compound. The absence of superconductivity in (C 2 H 8 N 2 ) 0.4 Fe 2 S 2 is mainly due to the external pressure on FeS layers induced by En intercalation. [ABSTRACT FROM AUTHOR]

151Eu and 153Eu Mössbauer spectroscopies have been used to study the magnetism of the Ni2+ moments in Eu2BaNiO5 by way of the exchange-induced Eu3+ moments. These independent and complementary probes indicate that at high temperatures all of the moments in the Haldane quantum spin chains are paramagnetic. On cooling below 25 K, fluctuations of ∼90% of the Ni2+ moments slow down, while the remaining 10% remain paramagnetic (indicating the presence of chain defects). Both 151Eu and 153Eu Mössbauer measurements yield the same Ni2+ moment. Furthermore, below 5 K, the 90% chain component becomes static and ordered, in excellent agreement with the ordering temperature expected from the rare-earth exchange energy. [ABSTRACT FROM AUTHOR]

Magnetic properties of sol-gel-prepared bulk samples of Co0.05Zn0.95O and Mn0.05Zn0.95O are reported before and after annealing in 5%H2/95%Ar at 573 K for 6 h. The as-prepared samples are paramagnetic with the magnetic susceptibility χ following the Curie-Weiss law: χ=χ0+C/(T-θ). The magnitudes of C are consistent with the magnetic moments expected for the Co2+ and Mn2+ states. After hydrogenation, the magnetism of Mn/ZnO is unchanged but Co/ZnO acquires room-temperature ferromagnetism (RTFM) with a magnetic moment of 0.35μB/Co site and hysteresis loop with coercivity Hc≃600 Oe, remanence Mr≃0.45 emu/g, and saturation magnetization Ms≃1.2 emu/g. Electron magnetic-resonance spectroscopy at 9.28 GHz gives signals corresponding to the Co2+ and Mn2+ states for the paramagnetic states and a broad FM signal for the hydrogenated Co/ZnO. This difference under hydrogenation between Co/ZnO and Mn/ZnO suggests that n-type doping leads to stabilizing of RTFM in Co/ZnO but not in Mn/ZnO, the latter perhaps requiring p-type doping. [ABSTRACT FROM AUTHOR]

The germanides RE3Pt4Ge6 (RE = Y, Pr, Nd, Sm, Gd-Dy) have been synthesized by arc-melting of the elements followed by inductive annealing to improve the crystallinity and allow for structural order. The compounds have been studied by powder X-ray diffraction; additionally the structure of Y3Pt4Ge6 has been refined from single-crystal X-ray diffractometer data. It exhibits a (3 + 1)D modulated structure, indicating isotypism with Ce3Pt4Ge6. The crystal structure can be described as an intergrowth between YIrGe2- and CaBe2Ge2-type slabs along [100]. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Y3Pt4Ge6 and Curie-Weiss paramagnetism for Pr3Pt4Ge6 and Nd3Pt4Ge6. Sm3Pt4Ge6 exhibits van Vleck paramagnetism, while antiferromagnetic ordering at TN = 8.1(1) K and TN = 11.0(1) K is observed for Gd3Pt4Ge6 and Tb3Pt4Ge6, respectively. [ABSTRACT FROM AUTHOR]

Magnetizabilities and magnetically induced ring-current strength susceptibilities have been calculated at the Hartree–Fock, density functional theory and second order Møller–Plesset levels for a number of antiaromatic closed-shell carbaporphyrins, carbathiaporphyrins and isophlorins. The calculations yield a linear relation between magnetizabilities and ring-current strength susceptibilities. The calculations show that the porphyrinoids with the largest ring-current strength susceptibility are closed-shell paramagnetic molecules with positive magnetizabilities. The closed-shell paramagnetism is due to the large paramagnetic contribution to the magnetizability originating from the strong paratropic ring current in the antiaromatic porphyrinoids. [ABSTRACT FROM AUTHOR]

FeTaCN films, prepared by using reactive sputtering, were studied for the application for soft underlayers of perpendicular media. As-deposited FeTaCN nanocrystalline films with a N[SUB2]/Ar ratio of 5% exhibited high saturation moment (B[SUBs] = 1.63 T) and low coercivity (1.4 Oe). IrMn/FeTaCN exchange-biased multilayer films and CoSm/FeTaCN hard-biased films were investigated to control the domain structure and magnetization reversal in FeTaCN films. Exchange bias field is inversely proportional to the thickness of FeTaCN films and reaches 11.4 Oe in the laminated sample of [IrMn (8 mm)/FeTaCN (50 nm)]×4. The interfacial coupling energy between IrMn and FeTaCN is 0.09 erg/cm[SUP2]. The biasing field of CoSm/FeTaCN can reach a maximum value of 10.6 Oe at the FeTaCN thickness of 200 nm. The corresponding interfacial coupling energy of FeTaCN/CoSm is as large as 0.27 erg/cm[SUP2]. [ABSTRACT FROM AUTHOR]

Dipole approximations are used to model up to three superparamagnetic particle systems as they assemble on magnetic island templates. It is shown that small variations in the ratio of particle-to-island diameter as well as the particle positions above the island can change magnetic forces from attractive to repulsive. This observation could potentially permit a template to be designed to promote single particle coverage of individual magnetic islands. [ABSTRACT FROM AUTHOR]

• Polycrystalline specimens of Ba 2 Y 1- x Cu x TaO 6-δ were synthesized by the solid-state reaction route. • The magnetic properties of the Ba 2 Y 1- x Cu x TaO 6-δ solid solutions were investigated and reported for the first time. • The Cu for Y substitution induces paramagnetism and the onset of antiferromagnetic correlations. We carried out a study of the structural and magnetic properties of Ba 2 Y 1- x Cu x TaO 6- δ (0.0 ≤ x ≤ 0.5) compounds. The cubic rock-salt double perovskite structure of Ba 2 YTaO 6 is retained upon the partial substitution of Cu for Y up to x = 0.50 and the lattice parameter a drops at the rate of da/dx ≈ −0.17 ± 0.01 Å/%Cu. While the effective moment μ eff and the Curie-Weiss temperature θ CW are nearly negligible in Ba 2 YTaO 6 , the partial substitution of Cu for Y results shows an increase in μ eff at the rate of ≈ 1.9 ± 0.2 µ B /%Cu, consistently with the paramagnetic behavior expected for Cu2+, and a decrease in θ CW at the rate of −16 ± 2 K/%Cu. The drive of θ CW towards more negative values is suggestive of the onset of antiferromagnetic correlations. [ABSTRACT FROM AUTHOR]

The mechanism of influence of molecular oxygen on the probability of ortho-para conversion of water molecules and its relation to water magnetization are considered within the framework of the concept of paramagnetic spin catalysis. Matrix elements of the hyperfine ortho-para interaction via the Fermi contact mechanism are calculated, as well as the Maliken spin densities on water protons in HO and O collisional complexes. The mechanism of penetration of the electron spin density into the water molecule due to partial spin transfer from paramagnetic oxygen is considered. The probability of ortho-para conversion of the water molecules is estimated by the quantum chemistry methods. The results obtained show that effective ortho-para conversion of the water molecules is possible during the existence of water-oxygen dimers. An external magnetic field affects the ortho-para conversion rate given that the wave functions of nuclear spin sublevels of the water protons are mixed in the complex with oxygen. [ABSTRACT FROM AUTHOR]

Experiments for vanadium dioxide show a magnetic transition characterized by a sharp variation in susceptibility associated with the metal-insulator transition at the temperature Tc. The sample is shown to be of Pauli paramagnetism above Tc but of anomalous paramagnetism below Tc. Considering co-contributions of Pauli paramagnetism of residual V4+ ions and Curie-like paramagnetism of V-V dimers, we propose a phenomenological expression for the temperature-dependent susceptibility below Tc, which yields an excellent agreement with the experimental data. The unusual temperature dependence of Curie-like susceptibility below Tc is explained to be due to the fact that every dimer is formed by spin paring at an angle θ close to 180° and hence has an effective spin expressed as Seff = cos (θ/2) which decreases with lowering temperature. The observed metal-insulator and magnetic transitions are argued to be due to a transition from the high-temperature Pauli paramagnetic state of V4+ ions to the low-temperature dimerized state. [ABSTRACT FROM AUTHOR]

We reported the magnetism, magnetic phase transition behavior and magnetocaloric effect of the ternary Dy 2 CuSi 3 and Ho 2 CuSi 3 compounds. A second order magnetic phase transition from a paramagnetic (PM) to ferromagnetic (FM) state around their respective Curie temperatures were confirmed by using the magnetic measurements and rescaled magnetic entropy change curves in both compounds. A large magnetic entropy change was obtained with the absence of thermal and magnetic hysteresis loss in both compounds. The maximal magnetic entropy change (-Δ S M max ) reach 18.3 and 28.3 J/kg K for a magnetic field change of 0–70 kOe in Dy 2 CuSi 3 and Ho 2 CuSi 3 , respectively. The corresponding values of relative cooling power ( RCP ) are evaluated to be 460 J/kg and 627 J/kg, respectively. [ABSTRACT FROM AUTHOR]

First-principles calculations have been performed to study the effect of C on the stacking fault energy (SFE) of paramagnetic γ -Fe and Fe Cr Ni austenitic steel. In these systems, the local magnetic structure is very sensitive to the volume in both fcc and hcp structures, which emphasizes the importance of the magnetovolume coupling effect on the SFE. The presence of C atom suppresses the local magnetic moments of Fe atoms in the first coordination shell of C. Compared to the hypothetical nonmagnetic case, paramagnetism significantly reduces the effect of C on the SFE. In the scenario of C being depleted from the stacking fault structure or twin boundaries, e.g. , due to elevated temperature, where the chemical effect of C is dissipated, we calculate the C-induced volume expansion effect on the SFE. The volume induced change in the SFE corresponds to more than ∼ 50% of the total C effect on the SFE obtained assuming uniform C distribution. [ABSTRACT FROM AUTHOR]

In this paper, we derive a new force–extension formula for stretched macromolecules and homogeneous polymer matrices. The Ising model arising from paramagnetism is employed, where the magnetic force is replaced by the external force, and the resistance energy is addressed in this model instead of the usual persistent length arising from the freely jointed chain and worm-like chain models. While the force–extension formula reveals the distinctive stretching features for stretched polymers, the resistance energy is found to increase almost linearly with the external force for our two polysaccharides stretching examples with and without ring conformational changes. In particular, a jump in the resistance energy which is caused by a conformational transition is investigated, and the gap between the jump determines the energy barrier between two conformational configurations. Our theoretical model matches well with experimental results undergoing no and single conformational transitions, and a Monte Carlo simulation has also been performed to ensure the correctness of the resistance energy. This technique might also be employed to determine the binding energy from other causes during molecular stretching and provide vital information for further theoretical investigations. [ABSTRACT FROM AUTHOR]

The magnetic forces between paramagnetic squares cannot be calculated using a classic dipolar model because the magnetic field distribution is not uniform within square particles. Here, we present the calculation of magnetic forces and torques on paramagnetic squares in a uniform 2-D magnetic field using a Laplace's equation solver. With these calculations, we simulate the variations in equilibrium configurations as a function of number of interacting squares. For example, a single square orients with its diagonal directed to the external field while a system of multiple squares will assemble into chain-like structures with their edges directed to the external field. Unlike chains of spherical magnetic particles, that easily stagger themselves to aggregate, chains consisting of magnetic squares are unable to aggregate due to interchain repulsion. [ABSTRACT FROM AUTHOR]

Deals with a study which developed computer codes for evaluating the induced magnetic form factors of fcc and bcc itinerant electron paramagnets. Background on uniform magnetic fields; Formulation of the magnetic response problem in real space; Results for bulk susceptibility.

Provides information on a study that presented results of calculations based on local spin density formalism of the magnetovolume properties of several compounds in the C15 structure such as ZrV[sub2], ZrZn[sub2] and TiBe[sub2]. Experimental procedure; Results and discussion.

Magnetic properties and magnetocaloric effect (MCE) in ErFeAl and HoFeAl intermetallic compounds have been studied systematically. Both compounds undergo a second order magnetic phase transition from paramagnetic to ferromagnetic state together with a probable spin reorientation transition at low temperature. A considerable reversible magnetocaloric effect was observed around its own Curie temperatures T C ∼55 K and 80 K for ErFeAl and HoFeAl, respectively. For a magnetic field change of 0–7 T, the maximum values of magnetic entropy change (−Δ S M max ) are found to be 8.3 and 9.9 J/kg K for RE = Er and Ho, respectively. The corresponding values of refrigerant capacity ( RC ) are evaluated to be 384 and 647 J/kg. [ABSTRACT FROM AUTHOR]

Compounds [Fe3Ln(tea)2(dpm)6] ( Fe3Ln; Ln= Tb-Yb, H3tea=triethanolamine, Hdpm=dipivaloylmethane) were synthesized as lanthanide(III)-centered variants of tetrairon(III) single-molecule magnets (Fe4) and isolated in crystalline form. Compounds with Ln=Tb-Tm are isomorphous and show crystallographic threefold symmetry. The coordination environment of the rare earth, given by two tea3− ligands, can be described as a bicapped distorted trigonal prism with D3 symmetry. Magnetic measurements showed the presence of weak ferromagnetic Fe ⋅⋅⋅Ln interactions for derivatives with Tb, Dy, Ho, and Er, and of weak antiferromagnetic or negligible coupling in complexes with Tm and Yb. Alternating current susceptibility measurements showed simple paramagnetic behavior down to 1.8 K and for frequencies reaching 10000 Hz, despite the easy-axis magnetic anisotropy found in Fe3Dy, Fe3Er, and Fe3Tm by single-crystal angle-resolved magnetometry. Relativistic quantum chemistry calculations were performed on Fe3Ln (Ln=Tb-Tm): the ground J multiplet of Ln3+ ion is split by the crystal field to give a ground singlet state for Tb and Tm, and a doublet for Dy, Ho, and Er with a large admixture of mJ states. Gyromagnetic factors result in no predominance of gz component along the threefold axis, with comparable gx and gy values in all compounds. It follows that the environment provided by the tea3− ligands, though uniaxial, is unsuitable to promote slow magnetic relaxation in Fe3Ln species. [ABSTRACT FROM AUTHOR]

• The Pb vacancies, O defects and Co ions induce room FM for PbPd 1-x Co x O 2. • F dopant can induce the changed valence states of O, Co and Pd ions. • The enhanced magnetization results mainly from Pd(2−δ)+ and more O1− induced by F. • A magnetization jump at 265 K is observed originate from valence state transformation between O1− and O2−. In this work, Co-doped and Co-F co-doped PbPdO 2 nanoparticles with a body-centered orthorhombic structure were synthesized via sol–gel method. The measured results reveal that, Pb and O vacancies exist in all samples; the valence state of magnetic atom Co is identified as mixed Co2+ and Co3+; all samples exhibit both ferromagnetism and paramagnetism; the incorporation of fluorine results in an evident increase in the magnetic moment of PbPd 0.875 Co 0.125 O 2 @F; a jump of magnetization at about 265 K can be found in both FC and ZFC curves of PbPd 1-x Co x O 2 (x = 0, 0.05, 0.10 and 0.115). Moreover, the origin of the magnetism can be considered as follows: the ferromagnetism for PbPd 1-x Co x O 2 (0 < x ≤ 0.15) results from the combined effect of O1− and magnetic Co ions; fluorine substitution in an oxygen lattice site and the fluorine doping in the interstitial sites can induce both distinct roles on the valence of oxygen, Co and Pd ions, which changes evidently the magnetic properties of PbPd 1-x Co x O 2. Fortunately, the magnetic properties of PbPdO 2 , Co-doped PbPdO 2 , Co-F co-doped PbPdO 2 can be verified by first-principles calculations. It is found that the enhanced magnetization results mainly from Pd(2−δ)+ and more O1− induced by F. Finally, the magnetization jump at about 265 K has been explained by the temperature-dependent valence transformation between O2− and O1−. [ABSTRACT FROM AUTHOR]

The external controllability of the magnetic properties in topological insulators would be important both for fundamental and practical interests. Here we predict the electric-field control of ferromagnetism in a thin film of insulating magnetic topological insulators. The decrease of band inversion by the application of electric fields results in a reduction of magnetic susceptibility, and hence in the modification of magnetism. Remarkably, the electric field could even induce the magnetic quantum phase transition from ferromagnetism to paramagnetism. We further propose a transistor device in which the dissipationless charge transport of chiral edge states is controlled by an electric field. In particular, the field-controlled ferromagnetism in a magnetic topological insulator can be used for voltage based writing of magnetic random access memories in magnetic tunnel junctions. The simultaneous electrical control of magnetic order and chiral edge transport in such devices may lead to electronic and spintronic applications for topological insulators. [ABSTRACT FROM AUTHOR]

The so-called “metal-radical approach” to the design of molecule-based magnetic materials relies on the availability of paramagnetic ligands that can reliably form coordination complexes with paramagnetic metal ions. While the most common radical ligands are based on nitroxides, other paramagnetic building blocks are also gaining attention. Thiazyls and their related selenazyls are promising candidates for the development of radical ligands and, because they have inherently interesting materials’ properties, their use as ligands has the potential to generate novel materials with unprecedented properties. Significant progress has been made in this field in the past ten years. This review is a timely look back at the development of the field, highlighting the diversity of complexes and designs, and a look forward to a promising future. [ABSTRACT FROM AUTHOR]

The transition between paramagnetism and ferromagnetism is the paradigm for a continuous phase transition at finite temperature. When such a transition is tuned to zero temperature in clean materials, the growth of low-energy zero-point fluctuations potentially drives an array of phenomena, including the formation of novel states such as non-conventional superconductivity. Experimentally, the growth of the fluctuations, however, is curtailed and the transition becomes discontinuous as its temperature is reduced. This is understood to arise from non-analytic corrections to the free energy that always occur. In a recent theory, changes of the excitation spectrum are self-consistently considered alongside the ground state. This analysis reveals that a transition to a new state may be an alternative outcome. As the excitation spectrum (the 'disorder') is pivotal to promoting the new 'order' this mechanism is referred to as 'order by disorder'. Here, we report the discovery of modulated order in PrPtAl, consistent with complex spirals, at the boundary between paramagnetism and ferromagnetism, giving the first clear experimental realization of such a state. [ABSTRACT FROM AUTHOR]

We report on the magnetic property of 0.67–WO 3 +0.33–VO x mixture film deposit on the corning glass substrate using the chemical sol–gel and atmospheric pressure chemical vapor deposition (APCVD) methods. The XRD and Raman spectroscopy confirm species of both materials, and the morphological studies with FIB-SEM and TEM reveal segregation of W and V atoms. XPS reveals that V 4+ from VO 2 forms only 11% of the film; V 3+ in the form of V 2 O 3 form 1% of the film, 21% is V 5+ from V 2 O 5 and 67% is given to W 6+ from WO 3 . The analysis of the ESR data shows some sharp changes in the magnetism near the metal-to-insulator (MIT), which could be theoretically interpreted as the ordering or alignment of electron spins from net moment nature to parallel alignment of magnetic moment. The derivatives of magnetic susceptibility established the thermally induced magnetic property: two distinct transitions of 339 K for heating data and 338 K for cooling data for 151.2 mT field were obtained. Similar results were also obtained for 308.7 mT field, 336 K for heating data and 335 K for cooling data. VSM results confirm a paramagnetic phase with a small amount of magnetically ordered phase. [ABSTRACT FROM AUTHOR]

In this work we investigate magnetic effects in terms of the translational and rotational invariances of magnetisation. Whilst Landau-type diamagnetism originates from translational invariance, a new diamagnetism could result from rotational invariance. Translational invariance results in only conventional Landau-type diamagnetism, whereas rotational invariance can induce a paramagnetic susceptibility for localised electrons and also a new kind of diamagnetism that is specific to conducting electrons. In solids, the moving electron shows a paramagnetic susceptibility but the surrounding screening of electrons may produce a new diamagnetic response by Lenz's law, resulting in a total susceptibility that tends to zero. For electricity, similar behaviours are obtained. We also derive the DC-type negative electric susceptibility via two methods in analogy with Landau diamagnetism. [ABSTRACT FROM AUTHOR]

The magnetic properties of 2H phase of MoS2 (2H-MoS2) and 1T phase of MoS2 (1T-MoS2) were investigated both experimentally and theoretically. Lithium (Li) intercalation method was used to prepare single-layer MoS2 sheets. It was found that pristine MoS2 (2H-MoS2) exhibited weak diamagnetism. After exfoliating by Li intercalation, the crystal structure transformed from 2H to 1T phase, and the magnetism was significantly enhanced from diamagnetism to paramagnetism accordingly. With further annealing in argon atmosphere, the 2H phase recovered gradually from 1T phase, and the magnetism decreased correspondingly. Using crystal field theory and combining the results of first principle calculation, we conclude that the enhanced magnetism can be attributed to the Mo atoms of 1T-MoS2. [ABSTRACT FROM AUTHOR]