AlFe2B2 was prepared by two alternative synthetic routes, arc melting and synthesis from Ga flux. In the layered crystal structure, infinite chains of B atoms are connected by Fe atoms into two-dimensional [Fe2B2] slabs that alternate with layers of Al atoms. As expected from the theoretical analysis of electronic band structure, the compound exhibits itinerant ferromagnetism, with the ordering temperature of 307 K. The measurement of magnetocaloric effect (MCE) as a function of applied magnetic field reveals isothermal entropy changes of 4.1 J kg(-1) K(-1) at 2 T and 7.7 J kg(-1) K(-1) at 5 T. These are the largest values observed near room temperature for any metal boride and for any magnetic material of the vast 122 family of layered structures. Importantly, AlFe2B2 represents a rare case of a lightweight material prepared from earth-abundant, benign reactants which exhibits a substantial MCE while not containing any rare-earth elements.

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Cobalt ferrite one-dimensional nanostructures (nanoribbons and nanofibers) were prepared by electrospinning combined with sol−gel technology. The nanoribbons and nanofibers were formed through assembling magnetic nanoparticles with poly(vinyl pyrrolidone) (PVP) as the structure-directing template. Nanoribbons and nanofibers were obtained after calcining the precursor nanoribbons at different temperatures. Successive Ostwald ripening processes occur during the formation of CoFe2O4 nanoribbons and nanofibers. The sizes of nanoparticles varied with calcination temperatures, which leads to different one-dimensional structures and variable magnetic properties. These novel magnetic one-dimensional structures can potentially be used in nanoelectronic devices, magnetic sensors, and flexible magnets.

Spinel ferrite, MFe 2O 4 (M = Co, Ni), ribbons with nanoporous structure were prepared by electrospinning combined with sol-gel technology. The ribbons were formed through the agglomeration of magnetic nanoparticles with PVP as the structure directing template. The length of the polycrystalline ribbons can reach millimeters, and the width of the ribbons can be tuned from several micrometers to several hundred nanometers by changing the concentration of precursor. The nanoporous structure was formed during the decomposition of PVP and inorganic salts. The ribbons exhibited weak saturation magnetizations and low coercivities at room temperature, but at low temperature, saturation magnetizations and coercivities increased a lot, especially for CoFe 2O 4 ribbons, reaching 72 emu/g and 1.45 T at 2 k, respectively. These novel magnetic ribbons can potentially be used in micro/nano electronic devices, gas-sensors, and catalysts.

Twelve new lanthanide copper heterobimetallic compounds, RE 2 Cu(TeO 3 ) 2 (SO 4 ) 2 (RE = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), with two different structural topologies, have been prepared by hydrothermal treatment. Both structure types crystallize in the triclinic space group, P1̅ , but the unit cell parameters and structures are quite different. The earlier RE 2 Cu(TeO 3 ) 2 (SO 4 ) 2 (RE = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm) share a common structural motif consisting of edge-sharing LnO 8 chains and [Cu-(TeO 3 ) 2 (SO 4 ) 2 ] 6− units. The later lanthanide version (Yb and Lu) is composed of edge-sharing LnO 7 dimers bridged by similar [Cu(TeO 3 ) 2 (SO 4 ) 2 ] 6− units. The change in the structure type can be attributed to the decreasing ionic radii of the lanthanides. The compounds containing RE 3+ ions with diamagnetic ground states (Y 3+ and Eu 3+ ) exhibit antiferromagnetic ordering at 12.5 K and 15 K, respectively, owing to the magnetic exchange between Cu 2+ moments. No magnetic phase transition was observed in all the other phases. The lack of magnetic ordering is attributed to the competing magnetic interactions caused by the presence of paramagnetic RE 3+ ions. The magnetism data suggests that substantial 3d−4f coupling only occurs in the Yb analogue.

Single crystals of the ternary clathrate-I Na8Al8Si38 were synthesized by kinetically controlled thermal decomposition (KCTD), and microcrystalline Na8Al8Si38 was synthesized by spark plasma sintering (SPS) using a NaSi + NaAlSi mixture as the precursor. Na8AlxSi46-x compositions with x ≤ 8 were also synthesized by SPS from precursor mixtures of different ratios. The crystal structure of Na8Al8Si38 was investigated using both Rietveld and single-crystal refinements. Temperature-dependent transport and UV/vis measurements were employed in the characterization of Na8Al8Si38, with diffuse-reflectance measurement indicating an indirect optical gap of 0.64 eV. Our results indicate that, when more than one precursor is used, both SPS and KCTD are effective methods for the synthesis of multinary inorganic phases that are not easily accessible by traditional solid-state synthesis or crystal growth techniques.

La 0.5 Ba 0.5 MnO 3 products with novel flowerlike, microcube, and nanocube structures were successfully synthesized by a simple hydrothermal route by controlling the alkalinity of the reaction solutions. The synthesized products were systematically studied by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results showed that the formation of the flowerlike structures with a layer assembly experienced a nucleation-aggregation-crystallization growth process, while the cubic structures experienced a nucleation-crystallization growth process due to the effect of different alkalinity in the reaction solutions. The higher alkalinity also led to a decrease in the size in the cubic structures. Suitable temperature and pressure were demonstrated to be crucial to the formation of the flowerlike structures by carrying out further control experiments. The measurement of the magnetic properties of three samples obtained at different alkaline conditions indicated that the size of the La 0.5 Ba 0.5 MnO 3 products had an obvious influence on their properties; however, the dependence of the properties upon the morphology of the La 0.5 Ba 0.5 MnO 3 products was minor.

Ternary intermetallics R 117 Co 52+δ Sn 112+γ (R = Y, La, Pr, Nd, and Ho) have been prepared by arc-melting followed by annealing at 800 • C. All the compounds belong to the Tb 117 Fe 52 Ge 112 structure type (space group Fm3m) characterized by a complex giant cubic unit cell with a~30 Å. The single-crystal structure determination of Y-and La-containing compounds reveals a significant structural disorder. A comparison of these and earlier reported crystal structures of R 117 Co 52+δ Sn 112+γ suggests that more extensive disorder occurs for structures that contain larger lanthanide atoms. This observation can be explained by the need to maintain optimal bonding interactions as the size of the unit cell increases. Y 117 Co 56 Sn 115 exhibits weak paramagnetism due to the Co sublattice and does not show magnetic ordering in the 1.8-300 K range. Ho 117 Co 55 Sn 108 shows ferromagnetic ordering at 10.6 K. Both Pr 117 Co 54 Sn 112 and Nd 117 Co 54 Sn 111 exhibit antiferromagnetic ordering at 17 K and 24.7 K, respectively, followed by a spin reorientation transition at lower temperature.