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Nanostructured transition metal dichalcogenide MnSe2 has attracted much attention due to its fascinating magnetic properties. In this article, a series of MnSe2 nanoparticles with different particle sizes are successfully prepared by a facile top‐down method of solid‐state reaction combined with ball milling, and the effects of ball milling on the phase composition, microstructure and magnetic properties of the MnSe2 are systematically studied. The results show that pure MnSe2 microparticles are obtained by the solid‐state reaction, however, partial MnSe2 is decomposed after ball milling for 16 h. The average particle size of the MnSe2 gradually decreases with the increase of milling time. MnSe2 nanoparticles with average particle size approximately 65 nm are obtained after milling for 40 h. After milling, the antiferromagnetic MnSe2 nanoparticles exhibit weak ferromagnetic characteristics due to the surface effect and the microstrain induced by ball milling. The residual magnetization (Mr) and coercivity (Hc) of the sample gradually increase as the particle size decreases. The Mr and Hc of the sample milled for 40 h reach 70.13 × 10−4 emu g−1 and 67.47 Oe, respectively. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe2O3) is known to undergo conversion from weak ferromagnetic to antiferromagnetic as the temperature decreases below the Morin temperature (TM = 250 K) due to spin moment rotation occurring during the Morin transition (MT). Herein, we endowed hematite with mesostructured chirality to maintain weak ferromagnetism without MT. Chiral mesostructured hematite (CMH) nanoparticles were prepared by a hydrothermal method with glutamic acid (Glu) as the symmetry-breaking agent. The triangular bipyramidal CMH nanoparticles were composed of helically cleaved nanoflakes with twisted crystal lattice. Field-cooled (FC) magnetization measurements showed that the magnetic moments of CMH were stabilized without MT within the temperature range of 10–300 K. Hysteresis loop measurements confirmed the weak ferromagnetism of CMH. The enhanced Dzyaloshinskii–Moriya interaction (DMI) was speculated to be responsible for the temperature-independent weak ferromagnetism, in which the spin configuration would be confined with canted antiferromagnetic coupling due to the mesostructured chirality of CMH. [ABSTRACT FROM AUTHOR]

Polycrystalline solid solutions of (1-x)PbTiO 3 -(x)Bi(Zn 0.5 Zr 0.5)O 3 [x = 0.10, 0.20, 0.30] have been synthesized by using solid state reaction method and followed by air annealing (AA)/ vacuum annealing (VA). All the samples show single phase perovskite structure with tetragonal symmetry (P4mm). Structural parameters are calculated using the Rietveld refinement technique. With the help of Scanning Electron Microscope (SEM), the surface morphology of all the samples is recorded at room temperature. The influence of VA on dielectric parameters such as dielectric constant and tangent loss of the synthesized samples are studied and compared with that of AA samples. These results unfold superior dielectric properties of VA samples as compared to AA samples. Intriguingly, the VA samples exhibit exotic ferromagnetism in non-magnetic PbTiO 3 –Bi(Zn 0.5 Zr 0.5)O 3 samples, transforming these into room temperature magneto-electric multiferroics. Besides, both the ferroelectric and ferromagnetic order parameters were found to increase with the increase in Bi(Zn 0.5 Zr 0.5)O 3 doping in PbTiO 3. The enhanced physical properties witnessed in VA PbTiO 3 –Bi(Zn 0.5 Zr 0.5)O 3 samples localized hopping of charge carriers confined to the grain. [ABSTRACT FROM AUTHOR]

By employing semi-flexible multi-N donor auxiliary ligands, namely 1,4-bis(5-pyrimidyl)benzene (bpmb) in conjunction with azide, novel Co(II) 2D coordination polymers have been successfully synthesized and structurally characterized, along with magnetic analysis. The resulting compound, {Co(N3)(bpmb)(H2O)2·H2O}n (1), exhibits a unique 2D structure comprised of interconnected Co(II) chains bridged by single end-to-end (EE) azide moieties. These chains are further linked by twisted trans-μ2-N,N′-bpmb auxiliary ligands, forming a grid-like network. Additionally, the layers are held together in a 3D arrangement through hydrogen bonding interactions between the coordination water and the N atom of the bpmb ligands. Importantly, magnetic investigations reveal that compound 1 displays weak ferromagnetism attributed to spin canting, with a critical temperature (Tc) of 12 K. [ABSTRACT FROM AUTHOR]

Mg-containing solid solutions based on Y2FeTaO7 and formed by various mechanisms of heterovalent substitution were synthesized and had the following compositions: Y2Fe0.55Mg0.3Ta1.15O7, Y2Fe0.625Mg0.3Ta1.075O7, Y2Fe0.7Mg0.3TaO7, Y2Fe0.7Mg0.2Ta1.1O7, Y2Fe0.85Mg0.15TaO7, Y1.85Mg0.15Fe0.925Ta1.075O7, and Y1.85Mg0.15FeTaO7. It was shown that all synthesized solid solutions have a pyrochlore-like layered structure (space group P3121), in which Fe3+ ions are distributed over three structural positions. The magnetic properties of these solid solutions are due to the presence of a small ferromagnetic component in a predominantly antiferromagnetic system and characterize a ferrimagnet or a canted antiferromagnet with the Néel transition at the Néel temperature TN above room temperature. According to the data of magnetic measurements, two magnetic phase transitions to the ordered phase occur in all the studied samples. Along with the TN transition, in weak magnetic fields and below TN, there is a second transition, which is most likely due to a spin reorientation of the Morin type. The existence of magnetic ordering at room temperature in one magnetic sublattice or an internal magnetic field (Hin) was confirmed by Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

Aromatic hydrocarbon molecules with π-conjugated structure have great potential for the search of exotic states such as high temperature superconductivity and novel quantum magnetism. In this work, we found that high temperature weak ferromagnetism can be achieved by intercalating rubidium into the shortest poly(para-phenylene) molecule—biphenyl. Both dc and ac magnetic susceptibility measurements showed that the synthesized material exhibits a typical antiferromagnetic transition at 48.5 K, accompanying a ferromagnetic character in the magnetically ordered region. Combining theoretical calculations and Raman spectroscopic studies, it was found that the mole ratio between rubidium and biphenyl is 1:1, and the molecular magnetic moments are formed by transferring the Rb-5s electrons to the C-2p orbitals. The weak ferromagnetism is produced by intralayer spin-canted antiferromagnetic and interlayer ferromagnetic spin couplings. Our finding enriches the physicochemical functionality of biphenyl and opens a window for the search of π-electron organic magnets in poly(para-phenylene) molecules.

To surmount the major concerns of commercial small molecule Gd chelates and reported Gd‐based contrast agents (GBCAs) for magnetic resonance imaging (MRI), a new concept of organogadolinium macrochelates (OGMCs) constructed from the coordination between Gd3+ and macromolecules is proposed. A library of macromolecules were screened for Gd3+ coordination, and two candidates [i.e., poly(acrylic acid) (PAA), and poly(aspartic acid) (PASP)] succeeded in OGMC formation. Under optimized synthesis conditions, both Gd‐PAA12 and Gd‐PASP11 OGMCs are outstanding T1‐weighted CAs owing to their super high r1 values (> 50 mm−1 s−1, 3.0 T) and ultralow r2/r1 ratios (< 1.6, 3.0 T). The ferromagnetism of OGMCs is completely different from the paramagnetism of commercial and reported GBCAs. The ferromagnetism is very weak (Ms < 1.0 emu g−1) leading to a low r2, which is preferred for T1 MRI. Gd3+ is not released from the OGMC Gd‐PAA12 and Gd‐PASP11, ensuring biosafety for in vivo applications. The safety and T1‐weighted MRI efficiencies of the OGMC Gd‐PAA12 and Gd‐PASP11 are tested in cells and mice. The synthesis method of the OGMCs is facile and easy to be scaled up. Consequently, the OGMC Gd‐PAA12 and Gd‐PASP11 are superior T1‐weighted CAs with promising translatability to replace the commercial Gd chelates. [ABSTRACT FROM AUTHOR]

Evolution of the structural, morphological and magnetic properties of Zn 1-x Mg x Fe 2 O 4 (X = 0.00, 0.10 and 0.20) nanoparticles are discussed in detail and relation between cation disorder and magnetic interactions are prospected. The synthesized samples sintered at 500 °C temperature under examination display cubic crystal structure possesses Fd-3m as space group. The average crystallite size and lattice parameter shows variation as revealed from scherrer equation with the addition of Mg dopant at zinc site. Rietveld refinement presented single phase formation. Raman spectroscopy was utilized to convey different Raman modes and their associated vibrations. Scanning electron microscopy was utilized to survey the morphological attributes. Magnetization studies reveal weak ferromagnetism at low temperature (5 K) due to cation disorder for all samples. Zero field cooled and field cooled curves from magnetization vs temperature reveal the blocking temperature and its dependence on cation disorder and particle size. These results provide information about the possible applications of zinc ferrite nanoparticles in magnetic sensors, nanomedicine, optoelectronics, and memory devices. • Pure and Mg doped ZnFe 2 O 4 nanoparticles were prepared by facile co-precipitation method. • Rietveld refinement confirms single phase with cubic crystal structure. • The synthesized samples show mixed spinel ferrite structures. • SEM images revealed that these nano-particles turn into agglomerates with increase in magnetic interactions. • Both MH and MT graphs reveals that synthesized samples show weak ferromagnetism. [ABSTRACT FROM AUTHOR]

By employing semi-flexible multi-N donor auxiliary ligands, namely 1,4-bis(5-pyrimidyl)benzene (bpmb) in conjunction with azide, novel Co(II) 2D coordination polymers have been successfully synthesized and structurally characterized, along with magnetic analysis. The resulting compound, {Co(N3)(bpmb)(H2O)2·H2O}n (1), exhibits a unique 2D structure comprised of interconnected Co(II) chains bridged by single end-to-end (EE) azide moieties. These chains are further linked by twisted trans-μ2-N,N′-bpmb auxiliary ligands, forming a grid-like network. Additionally, the layers are held together in a 3D arrangement through hydrogen bonding interactions between the coordination water and the N atom of the bpmb ligands. Importantly, magnetic investigations reveal that compound 1 displays weak ferromagnetism attributed to spin canting, with a critical temperature (Tc) of 12 K.

Abstract To surmount the major concerns of commercial small molecule Gd chelates and reported Gd‐based contrast agents (GBCAs) for magnetic resonance imaging (MRI), a new concept of organogadolinium macrochelates (OGMCs) constructed from the coordination between Gd3+ and macromolecules is proposed. A library of macromolecules were screened for Gd3+ coordination, and two candidates [i.e., poly(acrylic acid) (PAA), and poly(aspartic acid) (PASP)] succeeded in OGMC formation. Under optimized synthesis conditions, both Gd‐PAA12 and Gd‐PASP11 OGMCs are outstanding T1‐weighted CAs owing to their super high r1 values (> 50 mm−1 s−1, 3.0 T) and ultralow r2/r1 ratios (< 1.6, 3.0 T). The ferromagnetism of OGMCs is completely different from the paramagnetism of commercial and reported GBCAs. The ferromagnetism is very weak (Ms

[Display omitted] A series of layered solid solutions Y 2- x Fe 1+ x TaO 7 (x = 0–0.2) was synthesized and a structural transition (space group R 3 ¯ ↔ space group P 3 1 21) was observed at x = 0.1. In Y 2− x Fe 1+ x TaO 7 , which belongs to both structural types, geometrically frustrated 2D sublattices of kagome-type are formed, in which Fe3+ ions are coupled by short-range antiferromagnetic interactions, and the transition to the spin glass state is observed at T g ∼ 4.3 K. A phenomenon of weak ferromagnetism has been detected, the cause of which is probably a small tilt of the Fe3+ spins due to the Dzyaloshinskii–Moriya antisymmetric superexchange. [ABSTRACT FROM AUTHOR]

The detailed Raman scattering investigation of the lattice and spin dynamics of a single crystal of the F e 3 B O 6 antiferromagnet is reported. Azimuthally resolved polarization measurements provided an unambiguous determination of the symmetry of observed excitations. Low-temperature experiments at T = 4.2 K allowed us to reduce anharmonic contribution and deconvolute several overlapping phonon modes. Low-frequency measurements have made it possible to find two excitations at 13.1 and 16.6 cm − 1 , which were assigned to quasi-ferromagnetic and quasi-antiferromagnetic magnon excitations, respectively. The magnetic field applied along the hard-magnetization axis causes energy shifts of these excitations, but no spin-flip transition was observed up to B = 30 T. [ABSTRACT FROM AUTHOR]

There is an increase in demand of the next-generation spintronic devices with stable structural and magnetic properties in varying temperatures. An orthoferrites structure of the Pnma space group has been successfully prepared using high temperature solid-state reaction. In the Sm 2 Fe 2 O 5 + δ (SFO) material, F e 3 + ions occupy edge-cantered and face-cantered positions forming the tilted Fe O 6 octahedrons with Glazer's notation tilt a − a − c +. The ordering of the rare-earth ions at compensation temperature ( T comp = 2.3 K) , spin-flip transition in the range of 9.4 − 45.6 K , and a second-type spin-reorientation transition around the anisotropy barrier with lower and higher transitional temperatures, T L = 465 and T H = 480 K respectively. The canting of spins along with disordered spins at the surface results in a non-zero T comp and unsaturated magnetization. It is inferred that thermal activation of particle's moment over the anisotropy barriers (known as Kneller's law) only occurs above room temperature. [ABSTRACT FROM AUTHOR]

Polycrystalline Gd 2 NiIrO 6 double perovskite compound was synthesized by the solid-state route. Rietveld refinement of the X-ray diffraction pattern revealed that the compound was crystallized in a monoclinic structure with P 2 1 / n space group (IUCr. No. 14). The scanning electron micrograph showed that the grains were spherical and well distributed with an average grain size of around 1 μm. The temperature-dependent magnetic measurements showed magnetic transitions at 165 K and 149 K in the low-temperature region. Below the transition temperatures, weak ferromagnetism was evidenced by field-dependent magnetization measurements. Exchange bias effects were observed which were driven by Dzyaloshinsky–Moriya interactions in the compound. The UV–visible measurement evidenced that the compound had an optical band gap of 1.8 eV. The electronic structure calculations using the DFT + U method revealed that Gd 2 NiIrO 6 compound exhibited a bandgap only when on-site correlations for the d -states were included, and the calculation showed that the AF1 configuration was energetically favourable. [ABSTRACT FROM AUTHOR]

In the present work, we have synthesized La1‐xPbxMno3 (0 ≤ x ≤ 0.20) perovskites through a conventional solid‐state reaction route. The powder x‐ray diffraction data analyzed through the Rietveld refinement program confirm monophase rhombohedral distorted structure (R‐3c space group). Fourier transform infrared spectra exhibit strong and well‐defined absorption bands of a typical perovskite structure. The x‐ray photoelectron spectroscopy studies confirm the elemental composition and oxidation state of various elements in the samples. Low temperature resistivity measurements do not reveal metal–semiconductor transition (MST) in the pristine sample while Pb‐doped samples show MST. The metallic region of the temperature‐dependent resistivity data is well fitted with ρ(T) = ρο + ρ2.5T2.5, which reveals the significance of electron–magnon interaction. Moreover, the semiconducting behavior of all the samples follows the Mott's variable range hopping conduction process. Additionally, the semiconducting part is also fitted with the small‐polaron hopping (SPH) model that establishes the non‐adiabatic SPH mechanism obeyed for the lower doping, whereas adiabatic mechanism for the higher Pb concentration. Magnetic studies clearly indicate a paramagnetic to weak ferromagnetic transition associated with the Pb doping that may be due to the double‐exchange mechanism between the manganese ions via oxygen orbitals. The outcomes are elucidated on the basis of substitution effect induced by Pb2+ ions. [ABSTRACT FROM AUTHOR]

In the present work, we have synthesized La1‐xPbxMno3 (0 ≤ x ≤ 0.20) perovskites through a conventional solid‐state reaction route. The powder x‐ray diffraction data analyzed through the Rietveld refinement program confirm monophase rhombohedral distorted structure (R‐3c space group). Fourier transform infrared spectra exhibit strong and well‐defined absorption bands of a typical perovskite structure. The x‐ray photoelectron spectroscopy studies confirm the elemental composition and oxidation state of various elements in the samples. Low temperature resistivity measurements do not reveal metal–semiconductor transition (MST) in the pristine sample while Pb‐doped samples show MST. The metallic region of the temperature‐dependent resistivity data is well fitted with ρ(T) = ρο + ρ2.5T2.5, which reveals the significance of electron–magnon interaction. Moreover, the semiconducting behavior of all the samples follows the Mott's variable range hopping conduction process. Additionally, the semiconducting part is also fitted with the small‐polaron hopping (SPH) model that establishes the non‐adiabatic SPH mechanism obeyed for the lower doping, whereas adiabatic mechanism for the higher Pb concentration. Magnetic studies clearly indicate a paramagnetic to weak ferromagnetic transition associated with the Pb doping that may be due to the double‐exchange mechanism between the manganese ions via oxygen orbitals. The outcomes are elucidated on the basis of substitution effect induced by Pb2+ ions. [ABSTRACT FROM AUTHOR]

In the current investigation, the perovskite Y 1-x Nd x FeO 3 (x = 0, 0.05, 0.10, 0.15) polycrystalline powders were synthesized via sol-gel technique. SEM studies of the morphological and microstructural aspects revealed an increase in Nd3+ dopant concentration resulted in grain growth reduction from 0.7 μm to 0.2 μm. A comprehensive structural analysis involving XRD and Raman spectroscopy unveiled the structural distortion from the isovalent doping of Nd3+ ions at Y3+ sites with changes in lattice parameters. The doping led to a reduction in bandgap from 2.1 eV for pristine YFeO 3 to 1.78 eV for Y 0.85 Nd 0.15 FeO 3. While the magnetization increased on increasing Nd3+ doping concentration, the coercivity (H c) visibly reduced, as evidenced from the M-H loop studies. The A-B-K plots confirmed the transition from antiferromagnetic (AFM) behaviour (YFeO 3) to soft ferromagnetic (FM) behaviour (Y 1-x Nd x FeO 3 (x = 0.05, 0.10, 0.15)). In conclusion, we correlate the observed changes in optical and magnetic properties to the structural distortion. [ABSTRACT FROM AUTHOR]

The phase content and sequence, the crystal structure, and the magnetic properties of perovskite solid solutions of the (1-y)BiFeO3-yBiZn0.5Ti0.5O3 series (0.05 ≤ y ≤ 0.90) synthesized under high pressure have been studied. Two perovskite phases, namely the rhombohedral R3c and the tetragonal P4mm, which correspond to the structural types of the end members, BiFeO3 and BiZn0.5Ti0.5O3, respectively, were revealed in the as-synthesized samples. The rhombohedral and the tetragonal phases were found to coexist in the compositional range of 0.30 ≤ y ≤ 0.90. Magnetic properties of the BiFe1-y[Zn0.5Ti0.5]yO3 ceramics with y < 0.30 were measured as a function of temperature. The obtained compositional variations of the normalized unit-cell volume and the Néel temperature of the BiFe1-y[Zn0.5Ti0.5]yO3 perovskites in the range of their rhombohedral phase were compared with the respective dependences for the BiFe1-yB3+ yO3 perovskites (where B3+ = Ga, Co, Mn, Cr, and Sc). The role of the high-pressure synthesis in the formation of the antiferromagnetic states different from the modulated cycloidal one characteristic of the parent BiFeO3 is discussed. [ABSTRACT FROM AUTHOR]

The single-phase multiferroic Bi5Fe1 âˆ' x Ni x Ti3O15 (BFNT- x, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) ceramics were synthesized by a sol-gel auto-combustion method, and their microstructures, ferroelectric, magnetic, and dielectric properties were investigated in detail. All samples belong to layer-perovskited Aurivillius phase containing four perovskite units sandwiched between two Biâ€"O layers. Ni substitution can not only improve ferroelectricity but also enhance the magnetic properties. The BFNT-0.2 sample shows the largest remnant polarization (2 P r ∼ 11.6 ÎĽC/cm2) and the highest remnant magnetization (2 M r ∼ 0.244 emu/g). The enhancement of the magnetic properties may mainly originate from the spin canting of Fe/Ni-O octahedra via Dzyaloshinskiiâ€"Moriya (DM) interaction. In order to explore the influence of valance state of magnetic ions on the properties, the x-ray photoelectron spectroscopy was carried out. Furthermore, structural, ferroelectric, and magnetic transitions were also investigated. [ABSTRACT FROM AUTHOR]

The detailed Raman scattering investigation of the lattice and spin dynamics of a single crystal of the Fe3BO6 antiferromagnet is reported. Azimuthally resolved polarization measurements provided an unambiguous determination of the symmetry of observed excitations. Low-temperature experiments at T=4.2 K allowed us to reduce anharmonic contribution and deconvolute several overlapping phonon modes. Low-frequency measurements have made it possible to find two excitations at 13.1 and 16.6 cm−1, which were assigned to quasi-ferromagnetic and quasi-antiferromagnetic magnon excitations, respectively. The magnetic field applied along the hard-magnetization axis causes energy shifts of these excitations, but no spin-flip transition was observed up to B=30 T.

Intercalation of alkali metal is an effective way to tune the physicochemical property of polyaromatic hydrocarbons. Herein, we show for the first time that the weak ferromagnetism with a Curie temperature of 5.2 K can be realized in an all-carbon π-electron compound – potassium-intercalated 9-phenylanthracene. The magnetic measurements reveal that there exists an antiferromagnetic transition around 35 K before transition to the weak ferromagnetic phase. An in-depth theoretical investigation indicates that the weak ferromagnetism is produced by the intramolecular ferromagnetic and intermolecular antiferromagnetic spin couplings in the crystal unit cell. Our finding enriches the physical functionality of anthracene derivatives and adds a new member of organic magnetic materials. Potassium-intercalated 9-phenylanthracene exhibits a weak ferromagnetism in the low temperature region, manifested by a sudden increase of magnetic susceptibility at 5.2 K. Image 1 [ABSTRACT FROM AUTHOR]

Nanoparticles of hematite were prepared by the precipitation method. Structural, hysteresis, moment-temperature, ferromagnetic resonance tests were performed. All hematite peaks were appeared in the XRD pattern with corundum phase of crystallite size of 15 nm. The SEM images showed that the average particle size is around 21 nm with ribbed shape. Different Fe–O bond peaks were registered in the FTIR test. The sample showed weak ferromagnetic state as was checked by M-H and M-T tests. The M-H test showed opened loop at low-field region and linear behavior at high-field region with susceptibilities of 1.4 × 10−5 emu/g Oe and 7.5 × 10−6 emu/g Oe respectively. Fitting by Langevin equation is conducted to find the particle moment. Morin temperature was found to be 17.77 K, while Neel temperature was about 614 K. A comparison with literature was given. FMR test showed a shift in the resonance field with broadened line having Landé g factor of 1.90498 at 9.3 GHz. [ABSTRACT FROM AUTHOR]

The compound Mn2[VO4]F was synthesized using a hydrothermal synthesis route at low temperature and its crystal structure was determined from single crystal X-ray diffraction data. Mn2[VO4]F was characterized by magnetic susceptibility and specific heat capacity measurements. Mn2[VO4]F crystallizes with the triplite-type structure, space group C2/c, a = 13.451(3) Å, b = 6.6953(16) Å, c = 10.126(3) Å, β = 116.587(4)°, V = 815.6(3) Å3 and Z = 8. The structure consists of a 3D-framework built up of VO4 tetrahedra, and manganese (II) polyhedra which form chains running along the [101] and [010] directions. The coordination of the manganese cations and the connectivity between the manganese polyhedra are not defined clearly due to the disorder of the fluoride anions which form zigzag chains along [001]. The magnetic susceptibility follows a Curie–Weiss behavior above 50 K with Θ = −88 K indicating that predominant magnetic interactions are antiferromagnetic. The specific heat capacity and magnetization measurements show that Mn2[VO4]F undergoes a three-dimensional magnetic ordering at TN = 30 K and a canted weak ferromagnetism due to mixed-anion effect.

• Structure-properties (magnetic, electrical and thermal) relationship of Mn3Al alloy. • Observation of weak ferromagnetism buried in an antiferromagnet. • High value of electronic heat capacity. • Disordered system with strong frustration. Numerous interesting features of antiferromagnets open up the possibility of designing new antiferromagnetic materials that can be useful for spintronic device applications. Here we present the structural, magnetic, thermal and electrical transport properties of polycrystalline Mn 3 Al alloys prepared by arc melting. Rietveld refinement of the room temperature X-Ray diffraction patterns reveals that the arc-melted Mn 3 Al crystallizes in a β Mn phase (space group 213). Detailed analysis of the magnetic data suggests for a dominant antiferromagnetic ordering. However, an in-homogenous magnetic disorder is observed in the system having a weak ferromagnetic phase in the antiferromagnetic host. In spite of the strong spin fluctuations in this system, the signature of spin glass-like nature in these alloys are not observed as probed by the frequency-dependent AC-Susceptibility measurements. Furthermore, the heat capacity was insensitive to the applied field of 3 Tesla with a negligible magnetic contribution suggesting a large electronic contribution to the heat capacity in these alloys. This work provides a useful insight into the tunable physical properties of the Heusler alloys for exploring antiferromagnetic based spintronic applications. [ABSTRACT FROM AUTHOR]

The phase content and sequence, the crystal structure, and the magnetic properties of perovskite solid solutions of the (1−y)BiFeO3–yBiZn0.5Ti0.5O3 series (0.05 ≤ y ≤ 0.90) synthesized under high pressure have been studied. Two perovskite phases, namely the rhombohedral R3c and the tetragonal P4mm, which correspond to the structural types of the end members, BiFeO3 and BiZn0.5Ti0.5O3, respectively, were revealed in the as-synthesized samples. The rhombohedral and the tetragonal phases were found to coexist in the compositional range of 0.30 ≤ y ≤ 0.90. Magnetic properties of the BiFe1−y[Zn0.5Ti0.5]yO3 ceramics with y < 0.30 were measured as a function of temperature. The obtained compositional variations of the normalized unit-cell volume and the Néel temperature of the BiFe1−y[Zn0.5Ti0.5]yO3 perovskites in the range of their rhombohedral phase were compared with the respective dependences for the BiFe1−yB3+yO3 perovskites (where B3+ = Ga, Co, Mn, Cr, and Sc). The role of the high-pressure synthesis in the formation of the antiferromagnetic states different from the modulated cycloidal one characteristic of the parent BiFeO3 is discussed.

The ferri- and antiferromagnetic structures of a hureaulite-type synthetic compound, Mn2+5(PO4)2(PO3(OH))2(HOH)4, were elucidated by high-resolution neutron powder diffraction in combination with magnetic susceptibility and heat capacity measurements. At 6.17 K, the paramagnetic phase (space group: C2/c) transforms to inherit a ferrimagnetic order (magnetic space group: C2′/c′), followed at 1.86 K by an incommensurately modulated antiferromagnetic order (magnetic superspace group: P21/c.1′(α0γ)00s with the propagation vector k(0.523(2), 0, 0.055(1)). In the ferrimagnetic state, antiferromagnetic interactions are dominant for both intra and inter pentamers of Mn2+(O, HOH)6 octahedra. Differently aligned spin-canting sublattices seen in the ferrimagnetic models at 3.4, 4.5, and 6.1 K explain a weak ferromagnetism in the title compound. The observation of magnetic moments vigorously changing in a small temperature range of 6.1–1.5 K adumbrates a high complexity of interplaying structural and magnetic orders in this manganese phosphatic oxyhydroxide.

We report on the magnetic properties of disordered Li2Co2 – xNix(MoO4)3 (0 ≤ x ≤ 2) system with a lyonsite structure, where Li+, Ni2+, and Co2+ ions are distributed in a disordered manner in the trigonal prism and octahedral sites. All compositions were found to exhibit paramagnetic behavior at high temperature; the magnetic susceptibility was described by the modified Curie-Weiss law. The experimental effective moments were explained by spin and orbital contributions of the Co2+ ions and only the spin contribution for Ni2+ ions. The negative Curie-Weiss temperature θ indicates the existence of antiferromagnetic coupling for all compositions. At low temperature, the compounds with Co2+ ions (x = 0, 1, 1.6, and 1.8) exhibit a weak ferromagnetic state below 4 K due to intrinsic canting of antiferromagnetically coupled lattices. The compound containing only Ni2+ ions, Li2Ni2(MoO4)3, exhibits a pure antiferromagnetic behavior. [ABSTRACT FROM AUTHOR]

Magnetic properties of reduced T'-Pr2-xCexCuO4 (T'-PCCO) nanoparticles with x = 0, 0.10, and 0.15 have been investigated. The T'-PCCO samples were synthesized by the chemically dissolved method with HNO3 as dissolving agents and by the succeeding calcination at 1000 °C for 15 h in air. The reduced T'-PCCO samples were obtained by the reduction annealing at 700 °C for 10 h in Argon atmosphere and at 700 °C for 12 h in vacuum. Rietveld analyses of the X-ray diffraction (XRD) patterns for all the samples have revealed dependences of the c-axis length and the crystal size on the Ce doping and the reduction annealing. XRD analyses and transmission electron microscopy (TEM) images have confirmed T'-PCCO nanoparticles with the size of around 40–100 nm. Magnetic properties of all the T'-PCCO nanoparticles were studied by a superconducting quantum interference device (SQUID) showing a dominant paramagnetic feature with very weak ferromagnetism in the as-synthesized samples at room temperature. It has changed to a pure paramagnetic feature after the reduction annealing in argon atmosphere and an enhanced ferromagnetism through vacuum annealing. This is probably due to the change in the number of oxygen vacancies through the defect recovery and the removal of excess oxygen after both reduction annealing processes, respectively. [ABSTRACT FROM AUTHOR]

Abstract When Fe is doped in ZnO, a situation of charge imbalance is created due to the higher charge of Fe3+. A charge balance may be obtained by co-doping Li+ 0.5 Fe3+ 0.5 combinations. A solid solution of Zn 1- x (Fe 0.5 Li 0.5) x O (0 ≤ x ≤ 0.03125) is synthesized with this viewpoint. The crystallites belong to a wurtzite P6 3 mc space group, with lattice parameters a , b and c increasing nominally for x = 0.0156 and thereafter remaining invariant. The size varies in the range ~ 60–142 nm. Interstitials of Li and Zn ions are formed. Along with Fe3+ substitution these defects are reasons for O interstitials. These oxygen interstitials increase the red emission while reduction of oxygen vacancies reduces the green emission. These point defects create structural distortion and strain which can generate Zn vacancies. Bandgap reduces due to shallow defects. Mid-bandgap states due to oxygen interstitials and Fe 3d -O 2p hybridization result in NIR emission. On the other hand the crystal surface deforms due to Li addition which hardens the materials. A weak ferromagnetism appears at very low temperature which is enhanced by Li+ addition. Long range exchange mechanism between Fe3+ ions appears in the samples, mediated by magnetic polarons due to point defects. [ABSTRACT FROM AUTHOR]

Hybrid improper ferroelectric Ca3Ti2O7 (CTO) ceramics were synthesized by a solid‐state reaction method. Their polarization switching currents, dynamic processes of polarization‐switching, and leakage current properties were investigated. It was found that the dynamic polarization curves of CTO ceramics exhibit obvious dependence on the frequency of the driving electric fields. Moreover, CTO ceramics show a switchable diode effect. The underlying mechanism for the observed effects were proposed based on the interplaying between mobile charged defects and bound charges. The charged defects also lead to a decrease in the band gap of the CTO ceramic, as revealed by absorption spectrum analysis. [ABSTRACT FROM AUTHOR]

The iron(III) compound of composition [Fe(III)(salen)(2-Me-Him)]n, where H2salen = N, N′-ethylenebis(salicylaldimine) and 2-Me-Him = 2-methylimidazolate bridging ligand, was prepared. Magnetic resonance and magnetic susceptibility measurements showed the existence of linear and zigzag antiferromagnetic chains in the compound. Weak ferromagnetism was shown to arise in zigzag antiferromagnetic chains due to antisymmetric exchange interactions. The features of the temperature dependence of magnetization indicate that the magnetic system experiences the transition to the spin-glass state at a temperature below 30 K. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Single phased α-(Fe 2 O 3) 1−X (Cr 2 O 3) X nanoparticles were prepared. • Band gap of Fe 2 O 3 is narrowed to 1.6 eV with addition of Cr. • Pectin was used as a gelling agent for Sol-gel synthesis. • Nanoparticles stabilised in corundum structure with R-3C space group. • Weak ferromagnetism was observed for the prepares α-(Fe 2 O 3) 1−X (Cr 2 O 3) X (0 ≤ x ≤ 1). Abstract We report on the tunable band engineering in α-(Fe 2 O 3) 1−X (Cr 2 O 3) X nanoparticles. Nanoparticles were prepared by the sol-gel method and stabilised in the hexagonal crystal structure with R-3C space group. At room temperature band-gap studies have shown the narrowing of the band gap from 2.1 eV to 1.6 eV with Cr addition. Compared to antiferromagnetic α-Fe 2 O 3 nanoparticles, doping of Cr 2 O 3 increases the magnetic hysteresis significantly. Impedance spectroscopic studies have revealed Maxwell-Wagner dielectric relaxation near room temperature. Our results improve the understanding of the structural, optical, dielectric and magnetic properties of Cr-doped α-Fe 2 O 3 nanoparticles and illustrates that these nanoparticles have potential candidate in spintronic, optoelectronic, solar cell and photocatalysis applications. [ABSTRACT FROM AUTHOR]

Low dimension materials (especially antiferromagnetic nanoparticles) exhibit extraordinary magnetic properties, which are different from their bulk counterparts. Herein we report the synthesis of akaganeite nano-sticks by two different reaction pathways that enable good control on microstructure and surface properties, ensuring new application opportunities. Akaganeite nano-sticks prepared via conventional method have a length of 1.8 ± 0.15 µm and a diameter of 100 ± 20 nm with a smooth surface. Whereas modified method results in the synthesis of akaganeite nano-sticks with nanorods grown on their surface. Akaganeite nano-sticks produced by modified method have a length and diameter of 2.06 ± 0.02 µm and 160.26 ± 8.08 nm respectively. Ferromagnetism and near room temperature exchange biasing (250 K) was found in both the samples. The conventional method (AKN-0) demonstrates exchange biasing of 5700 A/m at 50 K whereas the modified method (AKN-2.5) shows 66275 A/m (approximately 11 times increased). XPS reveals defects generation in both methods, which results in the existence and enhancement of such magnetic properties. • Nanoscale antiferromagnetic materials shows different properties from their bulk counterpart. • Forced hydrolysis was used to synthesize 1-D β-FeOOH nanoparticles using two different synthesis routes. • Near room temperature exchange biasing and weak ferromagnetic effect was observed in antiferromagnetic akaganeite. • A correlation between defects generation and exchange biasing was developed and understood. [ABSTRACT FROM AUTHOR]

Magnetic properties of the high-pressure stabilized perovskite BiFe1-yScyO3 phases (0.1 ≤ y ≤ 0.9) have been studied by means of magnetization measurements and neutron diffraction. The metastable perovskites of this series undergo irreversible polymorphic transformations upon annealing, the phenomenon referred to as conversion polymorphism. It has been found that the solid solutions with y ≥ 0.70 exhibit no long-range magnetic ordering regardless of their polymorph modification, while those with y ≤ 0.60 are all antiferromagnets. Depending on the scandium content, temperature and structural distortions, three types of the antiferromagnetic orderings, involving collinear, canted and cycloidal spin arrangements, have been revealed in the phases obtained via conversion polymorphism and the corresponding magnetic phase diagram has been suggested.

Highlights • Magnetic moment of the Ima 2 phase of BiFe 0.5 Sc 0.5 O 3 is sensitive to uniaxial pressure. • A wide cusp-like anomaly of the magnetic susceptibility is observed below 200 K. • The initial magnetization is fitted as a sum of nonlinear and linear contributions. • The nonlinear contribution is dependent on both temperature and magnetic field. • An algorithm to minimize unwanted residual fields in the solenoid has been developed. Abstract Magnetic properties of new multiferroic BiFe 0.5 Sc 0.5 O 3 perovskite which exists in two different orthorhombic polymorphs, the antipolar Pnma and the polar Ima 2, were studied using a SQUID-magnetometer technique in magnetic fields up to 50 kOe in the temperature range of 5–300 K. Both polymorphs show a weak ferromagnetic component below the Néel temperature, T N ∼220 K. A wide cusp-like anomaly of the temperature dependent magnetic susceptibility was revealed below 200 K. The anomaly is dependent on the magnetic field applied and can be associated with the glassy magnetic behavior of the compound. The best fit of the initial magnetization curves taken at each temperature can be obtained as a sum of two contributions, namely the nonlinear in field and the linear one. The nonlinear contribution appeared to be temperature and magnetic field dependent, which is in a good agreement with the magnetization experimentally obtained as a function of temperature in different magnetic fields applied. Increase of external magnetic field leads to a decrease of the nonlinear contribution to the total magnetic moment. [ABSTRACT FROM AUTHOR]

Single phase samples of Gd 1−x Y x CrO 3 ( x  = 0.0–1.0) were prepared by sol-gel method. Lattice parameters obtained from the Rietveld refinement are found to decrease from a  = 5.3129 Å, b  = 5.5210 Å, and c  = 7.6040 Å for x  = 0 to a  = 5.2428 Å, b  = 5.5208 Å and c  = 7.5340 Å for x  = 1.0. The temperature variation of magnetization measurements show that all samples exhibit antiferromagnetic transitions and the Neel temperature ( T N ) decreases from T N  = 174 K for x  = 0.0 to 142 K for x  = 1.0. Interesting magnetization reversal behavior is observed as the temperature is lowered from T N under field cooled condition and the magnetic compensation temperature, T comp is found to decrease from 136 K for x  = 0 to 42 K for x  = 0.70. These samples exhibit tunable positive and negative exchange bias fields with a maximum negative value of −1.17 kOe for x  = 0.50. The origin of magnetization reversal and exchange bias field is explained by considering the competition between the paramagnetic moment of Gd 3+ ions under the influence of negative internal field and the weak ferromagnetic component of Cr 3+ ions due to canted antiferromagnetic ordering. [ABSTRACT FROM AUTHOR]

Single phase samples of bulk GdCr 1-x Fe x O 3 were prepared for x  = 0 to 0.50. The lattice parameters obtained from Rietveld refinement based on Pbnm space group show that they increase systematically with Fe concentration, i.e. with a  = 5.3145 Å, b  = 5.5249 Å and c  = 7.6068 Å for x  = 0 to a  = 5.3330 Å, b  = 5.5670 Å, and c  = 7.6382 Å for x  = 0.50. Magnetization measurement shows that all samples exhibit antiferromagnetic transition. Their Neel temperature ( T N ) gradually decreases upto x  = 0.20 and beyond that it increases quite sharply due to considerable concentration of Fe 3+ – O 2− – Fe 3+ networks. The magnetization reversal observed in the parent compound (GdCrO 3 ) is found to be suppressed upon Fe substitution and however for x  = 0.40, magnetic compensation is observed at T comp  = 125 K. They are explained by considering the variation in the magnitude of weak ferromagnetic moment for different Fe concentrations. Complex impedance spectra measured at different temperatures above room temperature show the thermally activated relaxation of charge carriers with contribution from both grains and grain boundaries. The relaxation frequency of charge carriers and dc conductivity follow the Arrhenius law with comparable activation energy values. [ABSTRACT FROM AUTHOR]

The Curie temperature of bulk and nanostructured Fe 5 Si 3 is investigated using experiments, density-functional simulations, and many-body model calculations. The bulk intermetallic, which crystallizes in the hexagonal D8 8 structure, exhibits several intriguing features: it does not exist as a room-temperature equilibrium phase, is close to the onset of ferromagnetism, and exhibits two crystallographically very different Fe sites. The samples, produced by rapid quenching (bulk) and cluster deposition (nanoparticulate thin films), have Curie temperatures of about 400 K. Interatomic exchange constants are calculated using the Kohn-Korringa-Rostoker (KKR) method and used to solve the multisublattice mean-field problem for the system. The Vienna ab initio simulation package (VASP) is employed to study the dependence of the Fe moment on the thermally induced spin misalignment, and a model calculation yields an estimate for quantum-spin-liquid corrections. The theory includes Heisenberg exchange but overestimates the Curie temperature, and a discussion is given regarding additional approaches to handle weakly ferromagnetic multisublattice intermetallic compounds. [ABSTRACT FROM AUTHOR]

The low temperature anomalous magnetic properties of a non-superconducting PrBCO 6+ x compound in an underdoped oxygen state of concentration ( x = 0.44) are characterized by paraprocess magnetic susceptibility χ H (T) measurements carried out as a function of temperature T under different values of a DC magnetic field H up to 110 kOe. The derivatives dχ H (T)/dT curves reveal a significant reduction with increasing H in the Néel temperature T N = 9 K of the Pr antiferromagnetic (AFM) ordering for which the transition subsists at 100 kOe. The small anomaly at T 2 = 6–7 K is confirmed at 20 kOe and the previous spin reorientation attributed to this transition temperature seems to be suppressed above 60 kOe. The well defined anomaly in the vicinity of the low-critical point T cr = 4–5 K which occurs simultaneously, is still present when the strength of H is increased up to 100 kOe. Weak field induced phase transitions are observed between T 2 and T N at a low transition-field (H t <11 kOe) in the differential magnetic susceptibility dM T (H)/dH as a function of H deduced from the isothermal magnetizations M T (H) with H up to 21 kOe, whereas a weak ferromagnetic behavior of the Pr sublattice appears below T cr . The magnetic field effects give rise to more evidence for the Pr-Cu(2) coupling with ‘exchange-frustrated AFM’ interactions and ascertain the main role of the Pr sublattice whereas the Cu(2) sublattice seems to be less efficient. [ABSTRACT FROM AUTHOR]

A new Co(II) complex, {[Co(MPA)(4,4′-bpy)(H 2 O)]·2H 2 O} n ( 1 ) (H 2 MPA = 4-methylphthalic acid, 4,4′-bpy = 4,4′-bipyridine), has been prepared under solvothermal condition and fully characterized. The X-ray crystallography test demonstrates that 1 exhibits two-dimensional (2D) layer structure in which the helical Co(II) chains linked by syn-anti carboxylate bridges are connected by 4,4′-bpy ligands. Weak ferromagnetism was observed on direct-current (dc) susceptibility due to the collective effects of the helical chain structure and antiferromagnetic couplings between Co(II) ions transmitted by μ 2 - 1,3-carboxylate groups. Interestingly, slow magnetic relaxation was observed in 1 at liquid helium temperatures without an external dc field. [ABSTRACT FROM AUTHOR]

Co 4 Nb 2 O 9 (CNO) having Co chains along c-direction shows gigantic magnetoelelctric coupling below antiferromagnetic ordering temperature of 27.3 K but above a spin flop field of 1.6 T. We have investigated the effect of substitution of 20% of isovalent magnetic Fe 2+ on magnetic and magnetoelectric properties. With Fe substitution, magnetization with temperature has shown a weak ferromagnetic behavior at low magnetic fields and antiferromagnetic like behavior at higher fields. Interestingly, linear magnetoelelctric and ferroelectric behaviors are evidenced in the Fe substituted samples but for an electric field as small as 5 kV/m and the magnetoelelctric coupling is ensured for magnetic fields as low as 0.25 T, which is far below the spin flop field. The reduction in single ion anisotropy of Co and modified Dzyaloshinkii-Moriya interactions with Fe appear to be important in inducing low field ME effect. [ABSTRACT FROM AUTHOR]

The compound Mn2[VO4]F was synthesized using a hydrothermal synthesis route at low temperature and its crystal structure was determined from single crystal X-ray diffraction data. Mn2[VO4]F was characterized by magnetic susceptibility and specific heat capacity measurements. Mn2[VO4]F crystallizes with the triplite-type structure, space group C2/c, a = 13.451(3) Å, b = 6.6953(16) Å, c = 10.126(3) Å, β = 116.587(4)°, V = 815.6(3) Å3 and Z = 8. The structure consists of a 3D-framework built up of VO4 tetrahedra, and manganese (II) polyhedra which form chains running along the [101] and [010] directions. The coordination of the manganese cations and the connectivity between the manganese polyhedra are not defined clearly due to the disorder of the fluoride anions which form zigzag chains along [001]. The magnetic susceptibility follows a Curie-Weiss behavior above 50 K with Θ = −88 K indicating that predominant magnetic interactions are antiferromagnetic. The specific heat capacity and magnetization measurements show that Mn2[VO4]F undergoes a three-dimensional magnetic ordering at TN = 30 K and a canted weak ferromagnetism due to mixed-anion effect. [ABSTRACT FROM AUTHOR]

Rubidium-intercalated biphenyl shows a high temperature weak ferromagnetism, manifested by a typical antiferromagnetic transition at 48.5 K and simultaneous existence of magnetic hysteresis in the magnetically ordered region. [Display omitted] • Rb-intercalated biphenyl is synthesized by low temperature solid phase reaction. • π-electron-based high temperature weak ferromagnetism is realized. • The magnetic moment is produced by transferring electron from Rb to biphenyl. Aromatic hydrocarbon molecules with π-conjugated structure have great potential for the search of exotic states such as high temperature superconductivity and novel quantum magnetism. In this work, we found that high temperature weak ferromagnetism can be achieved by intercalating rubidium into the shortest poly(para -phenylene) molecule—biphenyl. Both dc and ac magnetic susceptibility measurements showed that the synthesized material exhibits a typical antiferromagnetic transition at 48.5 K, accompanying a ferromagnetic character in the magnetically ordered region. Combining theoretical calculations and Raman spectroscopic studies, it was found that the mole ratio between rubidium and biphenyl is 1:1, and the molecular magnetic moments are formed by transferring the Rb-5s electrons to the C-2p orbitals. The weak ferromagnetism is produced by intralayer spin-canted antiferromagnetic and interlayer ferromagnetic spin couplings. Our finding enriches the physicochemical functionality of biphenyl and opens a window for the search of π-electron organic magnets in poly(para -phenylene) molecules. [ABSTRACT FROM AUTHOR]

We present an overview of the microscopic theory of the Dzyaloshinskii−Moriya (DM) coupling in strongly correlated 3d compounds. Most attention in the paper centers around the derivation of the Dzyaloshinskii vector, its value, orientation, and sense (sign) under different types of the (super)exchange interaction and crystal field. We consider both the Moriya mechanism of the antisymmetric interaction and novel contributions, in particular, that of spin−orbital coupling on the intermediate ligand ions. We have predicted a novel magnetic phenomenon, weak ferrimagnetism in mixed weak ferromagnets with competing signs of Dzyaloshinskii vectors. We revisit a problem of the DM coupling for a single bond in cuprates specifying the local spin−orbital contributions to the Dzyaloshinskii vector focusing on the oxygen term. We predict a novel puzzling effect of the on-site staggered spin polarization to be a result of the on-site spin−orbital coupling and the cation-ligand spin density transfer. The intermediate ligand nuclear magnetic resonance (NMR) measurements are shown to be an effective tool to inspect the effects of the DM coupling in an external magnetic field. We predict the effect of a strong oxygen-weak antiferromagnetism in edge-shared CuO 2 chains due to uncompensated oxygen Dzyaloshinskii vectors. We revisit the effects of symmetric spin anisotropy directly induced by the DM coupling. A critical analysis will be given of different approaches to exchange-relativistic coupling based on the cluster and the DFT (density functional theory) based calculations. Theoretical results are applied to different classes of 3d compounds from conventional weak ferromagnets ( α -Fe 2 O 3 , FeBO 3 , FeF 3 , RFeO 3 , RCrO 3 , …) to unconventional systems such as weak ferrimagnets (e.g., RFe 1 − x Cr x O 3 ), helimagnets (e.g., CsCuCl 3 ), and parent cuprates (La 2 CuO 4 , …).

A semi-flexible bipyrimidyl ligand, 5,5′-bipyrimidin (bpym), was used for the self-assembly of a transition metal coordination polymer, resulting in the formation of a nickel(II) compound, [Ni(Br)2(bpym)2]n (1) with a three-dimemsional (3D) structure. Single-crystal X-ray analysis showed that compound 1 crystallizes in the monoclinic space group C2/c and the structure represents a 3D (4,4)-connected bbe topological framework constructed of nickel(II) ions, twisted cis-μ-bpym and planar trans-μ-bpym groups. Magnetic characterization revealed that 1 shows antiferromagnetic coupling between the pyrimidyl-bridged Ni(II) ions along with weak ferromagnetism due to spin canting with a magnetic ordering below Tc = 3.4 K.