Structure and magnetic properties of Bi-doped calcium aluminosilicate glass microspheres

Bi-doped CaO–Al2O3–SiO2 glass microspheres with Ca2Al2SiO7 (gehlenite) composition were prepared by combination of solid-state reaction and flame synthesis. The concentration of Bi was 0.0, 0.5, 1 and 3 mol %. The chemical composition of prepared glass microspheres was determined by X-ray fluorescence (XRF). The structural and magnetic properties of prepared glass microspheres and their polycrystalline analogues were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectroscopy and SQUID magnetometry. The closer inspection of glass microspheres surface by SEM confirmed smooth surface and revealed no features indicating presence of crystalline phases. All Bi-doped microspheres are X-ray amorphous, however in case of undoped microspheres XRD detected traces of crystalline gehlenite. XRD analysis of samples crystallized at 1273 K for 10 h revealed the presence of gehlenite as the main crystalline phase. The presence of gehlenite in crystallized samples were also confirmed by Raman spectroscopy. All samples (glass microspheres and their crystalline analogues) showed diamagnetic or weak ferromagnetic behavior at room temperature, whereas paramagnetic or weak ferromagnetic behavior was observed at 2 K.

The Magnetic Susceptibility Bifurcation in the Ni-Doped Sb2Te3 Topological Insulator with Antiferromagnetic Order Accompanied by Weak Ferromagnetic Alignment

The magnetic susceptibility reveals a discontinuity at Néel temperature and a hysteresis loop with low coercive field was observed below Néel temperature. The magnetic susceptibility of zero field cool and field cool processes coincide at a temperature above the discontinuity, and they split at temperature blow the discontinuity. The magnetic susceptibility splitting is larger at lower external magnetic fields. No more magnetic susceptibility splitting was observed at a magnetic field above 7000 Oe which is consistent with the magnetic anisotropy energy. Our study supports that these magnetic susceptibility characteristics originate from an antiferromagnetic order accompanied by weak ferromagnetism.

A successive multi-phase transitions in polycrystalline BaFe2As2: Emergence of C4 phase

We report magnetization and resistivity studies on polycrystalline BaFe2As2 prepared by solid-state reaction, in the temperature range of 5–350 K, upto the field of 9 T. Low-field susceptibility exhibits multi-phase transitions with two new magnetic phase transitions beside the well-known transition at [Formula: see text] K from paramagnetic/antiferromagnetic-tetragonal/orthorhombic transitions. The phase at [Formula: see text] K is attributed to the phase transition from antiferromagnetic-orthorhombic (C2-phase) to antiferromagnetic-tetragonal phase (C4-phase), while the phase transition at higher temperatures remains unsolved. Making an analogy to the antiferromagnetic nanosized particles, we suggest that BaFe2As2 consists of smaller but similar nanosized clusters. We have analyzed the magnetization data using the modified Langevin function on the basis of thermally activated induced uncompensated spins (thermoinduced moments). The nanosized clustering in this compound is evidenced by the exchange bias and coercivity stemming from the exchange coupling interactions between weak ferromagnetic bulk magnetization in clusters and spin-glass-like phase interface layers surrounding the clusters. We also observe that annealing enhances the superconductivity, similar to the effect of pressure on the superconductivity. We find that an exponential term well describes the resistivity of this compound due to magnon-assisted interband electron–phonon scattering between the bands with [Formula: see text] and [Formula: see text] orbitals forming two-hole pockets around the zone center and one electron pocket around the zone corner. We have also obtained the Kadowaki–Woods ratio ([Formula: see text] cm (K mol/mJ)[Formula: see text] and the Sommerfeld–Wilson ratio ([Formula: see text]) for BaFe2As2, both ratios are much larger than those ([Formula: see text]/[Formula: see text] cm (K mol/mJ)2, [Formula: see text]) for Kondo lattice systems, indicating the existence of a weak ferromagnetic correlation between Fe moments. It appears that magnon-mediated pairing is responsible for superconductivity. Finally, we observe zero resistance at [Formula: see text] K in amorphous BaFe2As2, which gives a new insight into the superconductivity under very high pressure.

Structure–Property Relationships for Weak Ferromagnetic Perovskites

Despite several decades of active experimental and theoretical studies of rare-earth orthoferrites, the mechanism of the formation of their specific magnetic, magnetoelastic, optical, and magneto-optical properties remains a subject of discussion. This paper provides an overview of simple theoretical model approaches to quantitatively describing the structure–property relationships—in particular, the interplay between FeO6 octahedral deformations/rotations and the main magnetic and optic characteristics, such as Néel temperature, overt and hidden canting of magnetic sublattices, magnetic and magnetoelastic anisotropy, and optic and photoelastic anisotropy.

[CrIII8NiII6]n+ Heterometallic Coordination Cubes

Three new heterometallic [CrIII8NiII6] coordination cubes of formulae [CrIII8NiII6L24(H2O)12](NO3)12 (1), [CrIII8NiII6L24(MeCN)7(H2O)5](ClO4)12 (2), and [CrIII8NiII6L24Cl12] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [CrIIIL3] and the corresponding NiII salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight CrIII and six NiII ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the CrIII and NiII ions, with JCr-Ni = + 0.045 cm−1. EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the CrIII ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both CrIII and NiII ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)–(3) join the previously published, structurally related family of [MIII8MII6] cubes, where MIII = Cr, Fe and MII = Cu, Co, Mn, Pd.

[CrIII8NiII6]n+ Heterometallic Coordination Cubes

Three new heterometallic [CrIII8NiII6] coordination cubes of formulae [CrIII8NiII6L24(H2O)12](NO3)12 (1), [CrIII8NiII6L24(MeCN)7(H2O)5](ClO4)12 (2) and [CrIII8NiII6L24Cl12] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [CrIIIL3] and the corresponding NiII salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight CrIII and six NiII ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the CrIII and NiII ions, with JCr-Ni = +0.045 cm-1 . EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the CrIII ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both CrIII and NiII ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)-(3) join the previously published, structurally related family of [MIII8MII6] cubes, where MIII = Cr, Fe and MII = Cu, Co, Mn, Pd. <br>

[CrIII8NiII6]n+ Heterometallic Coordination Cubes

Three new heterometallic [CrIII8NiII6] coordination cubes of formulae [CrIII8NiII6L24(H2O)12](NO3)12 (1), [CrIII8NiII6L24(MeCN)7(H2O)5](ClO4)12 (2) and [CrIII8NiII6L24Cl12] (3) (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [CrIIIL3] and the corresponding NiII salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight CrIII and six NiII ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on (1) reveal weak ferromagnetic interactions between the CrIII and NiII ions, with JCr-Ni = +0.045 cm-1 . EPR spectra are consistent with weak exchange, being dominated by the zero-field splitting of the CrIII ions. Excluding wheel-like structures, examples of large heterometallic clusters containing both CrIII and NiII ions are rather rare, and we demonstrate that the use of metalloligands with predictable bonding modes allows for a modular approach to building families of related polymetallic complexes. Compounds (1)-(3) join the previously published, structurally related family of [MIII8MII6] cubes, where MIII = Cr, Fe and MII = Cu, Co, Mn, Pd. <br>

Multifunctionality of weak ferromagnetic porphyrin-based MOF: selective adsorption in liquid and gas phase

In the endless possibility space of metal organic framework design and development, the quest for new multifunctional materials with desirable properties is still ongoing. At the environmental level, their development...