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Magnetic properties of oleic acid/oleylamine coated magnetite nanoparticles of average diameter D=4, 6, 8, 10, and 12 nm are reported. The samples were characterized by transmission electron microscopy and x-ray diffraction (XRD) with XRD showing increasing disorder with decreasing D. Magnetization M vs temperature T data show the blocking temperature TB decreasing with decreasing D from TB=38 K for 12 nm to TB=6.5 K for D=4 nm. The saturation magnetization Ms at 2 K also decreases from Ms=62 emu/g for 12 nm to Ms=17 emu/g for 4 nm but the coercivity at 2 K increases with a decrease in D. It is shown that Ms fits Ms=92(1-2d/D)3 with d=0.68 nm for D>4 nm and d=0.86 for D=4 nm. This equation is derived assuming a core-shell model with shell of thickness d consisting of disordered spins not contributing to Ms. [ABSTRACT FROM AUTHOR]

Starting with 7 nm γFe2O3 nanoparticles, synthesis of DNA-γFe2O3 nanocomposite and its structural/magnetic properties vis-a-vis the parent γFe2O3 are reported. Analysis of the x-ray diffraction shows an increase in the particle strain and average particle size (to 9.7 nm) in DNA-γFe2O3 nanocomposite. Transmission electron microscopy also shows an increase in size and a considerably wider size distribution. Temperature (5–300 K) variation of the magnetization (M) shows a wider distribution of the blocking temperatures (TB), as expected from the wider size distribution. Above TB, the data of M vs H fit the modified Langevin function with magnetic moment/particle μp≈11 000μB, somewhat larger than μp≈8000μB for the parent γFe2O3. However, M/g(γFe2O3) is not significantly affected. In electron magnetic-resonance spectroscopy at 9.28 GHz, only a single line is observed in DNA-γFe2O3 nanocomposite compared to two lines in γFe2O3. These effects are discussed in terms of the above structural differences. [ABSTRACT FROM AUTHOR]

• Superconducting properties of polycrystalline FeSe 1 − x S x S x (x = 0.1 and 0.2) alloys are investigated. • Impact of external hydrostatic pressure and chemical pressure on the superconducting state. • Anomalous behavior of superconducting transition temperature. • Non-Fermi liquid type behavior of normal state resistivity. • Signature of flux flow resistance in the isothermal resistivity data as a function of external magnetic field. Here we report on the magnetic and magneto-transport behavior of Fe-based superconductor with nominal compositions FeSe 1 − x S x (x = 0.1 and 0.2). The impact of external hydrostatic pressure (P) and chemical pressure on the superconducting state of the FeSe system has been investigated in this work. Superconducting transition temperature (T c) is found to be shifted towards higher temperatures with 10% S doping at the Se site of the FeSe alloy. On further increase in the doping concentration (for x = 0.2), the superconducting T c decreases. We have also observed a significant effect of external P on the superconducting properties of these S-doped alloys. Different superconducting parameters calculated from our experimental data confirm the type-II superconducting nature of the studied compounds. The signature of flux flow resistance is observed in the isothermal resistivity data as a function of the external magnetic field. [ABSTRACT FROM AUTHOR]

Ground state magnetic properties of Eu 0.5 Sr 0.5 Mn 1− x Co x O 3 ( x = 0, 0.02, 0.05, and 0.1) with perovskite structure were investigated through dc magnetization and ac susceptibility measurements. Smaller ionic radii of Eu +3 ion makes the ground state magnetic properties of these compounds more interesting. The samples show magnetic memory, large relaxation, frequency-dependent ac susceptibility and aging effects at low temperature, which indicate glassy magnetic ground state in the studied samples. A gradual transition from the spin-glass like ground state to cluster-glass state is also observed with increasing Co concentration. This observation is due to the decrease in double exchange interaction between Mn 3+ and Mn 4+ ion and hence the ferromagnetic interaction with Co doping. [ABSTRACT FROM AUTHOR]

• Structural and magnetic properties of skyrmionic system, Cu 2 OSeO 3 are investigated. • Thermal hysteresis between FC and FCH data is observed. • Lattice distortion at the magnetic transition is noticed. • Large MCE is found near the ferrimagnetic transition for a small change in magnetic field. • The observed anomalous change in Cu(1)-Cu(2) distances tune the strength of the magnetic exchange interactions. [Display omitted] We report here the detailed investigation on structural and magnetic behavior of the polycrystalline sample of Cu 2 OSeO 3. The Mott insulator Cu 2 OSeO 3 is a fascinating material showing skyrmionic state and magneto-electric coupling. We observe clear signature of thermal hysteresis between field-cooled and field-cooled heating data in the low-field magnetization versus temperature curve just below the magnetic ordering temperature of T C ~ 60 K. Temperature dependent powder x-ray diffraction data indicate the presence of lattice anomaly below T C. The sample also shows reasonable value of conventional magnetocaloric effect for small value of applied magnetic field, which can be related to the change in the magnetic structure with field. [ABSTRACT FROM AUTHOR]

A number of studies on zinc ferrite (ZnFe 2 O 4) as photocatalyst in cleaning wastewater have been achieved, because zinc ferrite nanoparticles are less toxic, chemically stable, possess high magnetic crystalline anisotropy, high coercivity, good magnetization, are biocompatible and cost-effective. Besides, separation of zinc ferrite photocatalyst is facile due to its magnificent magnetic behavior. The current review addresses zinc ferrite as a promising photocatalyst, its magnetic properties and electronic structure. Furthermore, various synthesis techniques have been reviewed viz. hydrothermal, sol-gel, polyol, co-precipitation, microwave, solvothermal, microemulsion, etc. for zinc ferrite photocatalysts. Various strategies for enhancing photocatalytic performances of heterojunctioned zinc ferrite photocatalysts were thoroughly reviewed. In conclusion, challenges and upcoming research requirements in edict to improve photocatalytic applications of zinc ferrite photocatalysts are addressed. [Display omitted] • An outline on ZnFe 2 O 4 based photocatalysts is presented. • The structure and magnetic properties of ZnFe 2 O 4 based photocatalysts are discussed. • Photocatalytic applications are explored comprehensively. • Future outlook on ZnFe 2 O 4 based photocatalysts is reviewed. [ABSTRACT FROM AUTHOR]

• Systematic variation of the magnetic properties of Dy-In intermetallic compounds. • Observation of large magnetocaloric effect in compositions having large Dy concentration. • Thermal hysteresis and first order magnetic phase transition. • Signature of metamagnetism in the transport and magneto-caloric data. A comparative study of the magnetic and transport properties of three Dy-In intermetallic compounds, namely DyIn 3 , Dy 5 In 3 and Dy 3 In, is reported. DyIn 3 has cubic crystal structure; on the other hand, Dy 5 In 3 and Dy 3 In crystallize in tetragonal structure, albeit with different space groups. DyIn 3 orders antiferromagnetically below T N = 23 K, while Dy 5 In 3 and Dy 3 In show ferromagnetic-like ground state with much higher ordering temperatures (119 and 125 K respectively). The ferromagnetic compounds show significant magneto-caloric effect around their respective Curie temperatures. On the other hand, the magneto-caloric effect in DyIn 3 is low but associated with the change in sign around T N . All the samples show small magneto-resistance, and it is found to be positive in case of DyIn 3 at 5 K. The signature of metamagnetic transition in DyIn 3 is visible in the magneto-caloric and magneto-resistance data. Efforts have been made to account the observed magnetic phenomena based on Dy concentration and Dy-Dy bond distance in these three compositions. [ABSTRACT FROM AUTHOR]

We have performed magnetic and transport measurements on La[sub 0.67]Ca[sub 0.33]MnO[sub 3] polycrystalline and partially melted samples. The magnetization and resistance decrease as sintering temperature is increased. The insulator-to-metal transition temperature is remarkably enhanced in the partially melted sample, enabling its possible applications at room temperature. The microscopic studies in melt samples show an excellent connectivity between grains, suggesting the enhancement of percolative transport by opening new conduction channels and the disappearance of magnetic phase boundary at elevated temperature by the ordering of Mn spins blocked at the grain boundary of sintered samples. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Sn-doped MnNiGe alloy of nominal composition MnNiGe 0.915 Sn 0.085 has been examined through structural and magnetic investigations. Sn-doping stabilizes the hexagonal structure (with P 6 3 / m m c space group) at room temperature. On cooling from room temperature, it first orders antiferromagnetically (with commensurate structure) around 185 K. Further cooling results in a structural change of martensitic type around 145 K. The observed structural transition is also found to be associated with a simultaneous magnetic transition from high temperature commensurate antiferromagnetic state to low temperature incommensurate antiferromagnetic state. Both conventional and inverse magnetocaloric effect (MCE), with peak values of −6.01 J/kg-K and 6.56 J/kg-K for 0 to 5 tesla of changing magnetic field, have been visible around the magnetic and structural transitions, respectively. A significant effect of external hydrostatic pressure on the magnetic and MCE behaviors has also been observed. • Sn-doped MnNiGe alloy stabilizes hexagonal (P 6 3 / m m c) structure at room temperature. • Sn-doping results in a significant decrease in martensitic transition temperature. • Both conventional and inverse magnetocaloric effects (MCE) have been observed. • External hydrostatic pressure affects significantly on magnetic and MCE behavior. [ABSTRACT FROM AUTHOR]

Systematic investigations on Ag-doped MnNiGe alloys of nominal compositions MnNi 1 − x Ag x Ge (x = 0.10, 0.15 and 0.20) have been performed through dc magnetic measurements in ambient as well as in high pressure conditions. All the Ag-doped alloys undergo martensitic type structural phase transition with a monotonic decrease in transition temperature with increasing Ag concentration. Room temperature x-ray powder diffraction data confirm the presence of both hexagonal and orthorhombic phase for 10% Ag-doped alloy whereas, 15% and 20% Ag-doped alloys are found to be purely hexagonal in nature. Gradual incorporation of ferromagnetic interaction with increasing Ag-concentration in otherwise antiferromagnetic alloy is clear from the magnetic investigations. Application of external hydrostatic pressure further favors ferromagnetism. In addition, these Ag-doped alloys also show a reasonably high magnetocaloric effect around the magnetic and structural transition temperatures which makes these alloys important for magnetic cooling applications. The robustness of the observed magnetocaloric properties have also been checked by high pressure measurements. • Non-magnetic Ag has been doped in the Mn site of MnNiGe alloy. • The studied alloys undergo first order magneto-structural transition. • Ag-doping induces ferromagnetism in otherwise antiferromagnetic alloys. • The sample shows a large magneto-caloric effect. • Effect of external hydrostatic pressure on the magnetic properties is studied. [ABSTRACT FROM AUTHOR]