Surface Effects on the Magnetic Behavior of Nanocrystalline Nickel Ferrites: The Effect of Surface Roughness and Dilution

2005 ◽  
Vol 877 ◽  
Author(s):  
H. Nathani ◽  
R.D.K. Misra ◽  
W.F. Egelhoff
Keyword(s):  
Surface Roughness ◽  
Nickel Ferrite ◽  
Magnetic Measurements ◽  
Magnetic Behavior ◽  
Magnetic Data ◽  
Zero Field ◽  
Nanocrystalline Nickel ◽  
Polyethylene Matrix ◽  
Dilution Effects ◽  
Field Cooling

AbstractThe paper describes the surface roughness and dilution effects on the magnetic behavior of nanocrystalline nickel ferrites studied by SQUID magnetometer. Two different kinds of measurements were performed: (a) zero-field cooling (ZFC) and field cooling (FC) magnetization versus temperature and (b) magnetization as a function of the applied field. The analysis of magnetic measurements indicate that while the superparamagnetic behavior is retained by nanocrystalline ferrites of different surface roughness (0.8-1.8 nm) at 300K, the hysteresis loop at 2K becomes non-squared and the coercivity increases with increase in surface roughness. This behavior is discussed in terms of broken bonds and degree of surface spin disorder. In diluted dispersion systems containing 10-40% nickel ferrite in a polyethylene matrix, the interparticle attractions continue to be dominant even when the concentration of nickel ferrite is 10 wt.% in the diluted system. The general magnetic behavior of diluted dispersion system is similar to the undiluted system; however, coercivity, remanence, and saturation magnetization are altered. These changes in the magnetic data are ascribed to magnetization interactions that encourage flux closure configuration.

Magnetic behavior of nanocrystalline nickel ferrite

2005 ◽  
Vol 121 (1-2) ◽  
pp. 126-136 ◽  
Author(s):  
H. Nathani ◽  
S. Gubbala ◽  
R.D.K. Misra
Keyword(s):  
Nickel Ferrite ◽  
Magnetic Behavior ◽  
Nanocrystalline Nickel

Synthesis and Characterization of the Heptanuclear [MnIII 6 CoIII]3+ Triplesalen Complex: Evidence for Exchange Pathways Involving Low-spin CoIII

2010 ◽  
Vol 65 (3) ◽  
pp. 295-303 ◽  
Author(s):  
Erich Krickemeyer ◽  
Veronika Hoeke ◽  
Anja Stammler ◽  
Jürgen Schnack ◽  
Hartmut Bögge ◽  
...  
Keyword(s):  
Exchange Interaction ◽  
Metal Ion ◽  
Magnetic Measurements ◽  
Variable Temperature ◽  
Molecular Structures ◽  
Magnetic Data ◽  
Zero Field ◽  
Central Metal ◽  
Zero Field Splitting ◽  
Isotropic Exchange

The reaction of the tert-butyl-substituted triplesalen ligand H6talent-Bu2 with MnII(OAc)2・ 4H2O and K3[CoIII(CN)6] results in the formation of the heptanuclear complex [{(talent-Bu2 )- (MnIII(MeOH))3}2{CoIII(CN)6}](PF6)2(OAc)・11MeOH ([MnIII6 CoIII](PF6)2(OAc)・11MeOH, 1 ・11MeOH), which has been characterized by FT-IR spectroscopy, elemental analysis, ESI-MS, single-crystal X-ray diffraction, and magnetic measurements. The molecular structure of the [MnIII6 CoIII]3+ complex is closely related to the already published analogs [MnIII6CrIII]3+ and [MnIII6 FeIII]3+. Variable-temperature variable-field and μeff vs. T magnetic data have been analyzed in detail by full-matrix diagonalization of the appropriate spin-Hamiltonian consisting of isotropic exchange, zero-field splitting, and Zeeman interaction, taking into account the relative orientation of the D tensors. This allowed a careful inspection of the MnIII-MnIII exchange interaction involving a diamagnetic central metal ion. A satisfactory reproduction of the magnetic data required the incorporation not only of an exchange interaction between the MnIII ions belonging to one triplesalen half unit, but also of an exchange coupling between MnIII ions belonging to different triplesalen subunits. Satisfactory reproduction of the experimental data has been obtained for the parameter set J1 = −(0.50±0.04) cm−1, J2 = +(0.05±0.02) cm−1, and D = −(2.5±0.5) cm−1. A detailed analysis of the J1 coupling taking into account the molecular structures of the three available heptanuclear complexes [MnIII6MIII]3+ (M = Cr, Fe, Co) indicates that the exchange interaction between the MnIII ions belonging to the same triplesalen subunit involves not only an exchange pathway through the central phloroglucinol unit but also an exchange pathway through the central metal ion.

Structural, Magnetic and Hyperfine Properties of Molybdenum Dioxide-Hematite Mixed Oxide Nanostructures

MRS Advances ◽  
2018 ◽  
Vol 3 (47-48) ◽  
pp. 2887-2892
Author(s):  
Richard Trotta ◽  
Felicia Tolea ◽  
Mihaela Valeanu ◽  
Lucian Diamandescu ◽  
Agnieszka Grabias ◽  
...  
Keyword(s):  
Ball Milling ◽  
Milling Time ◽  
Mechanochemical Activation ◽  
Magnetic Measurements ◽  
Activation Process ◽  
Zero Field ◽  
Molybdenum Dioxide ◽  
Nanoparticle System ◽  
Ball Milling Time ◽  
Field Cooling

ABSTRACTMoO2-Fe2O3 nanoparticle system was successfully synthesized by mechanochemical activation of MoO2 and α-Fe2O3 equimolar mixtures for 0-12 hours of ball milling time. The study aims at exploring the formation of magnetic oxide semiconductors at the nanoscale. X-ray powder diffraction (XRD), Mössbauer spectroscopy and magnetic measurements were used to study the phase evolution of MoO2-Fe2O3 nanoparticle system under the mechanochemical activation process. The Mössbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextet and a doublet upon duration of the milling process with molybdenum dioxide. Recoilless fraction was determined using our dual absorber method and was found to decrease with increasing ball milling time. Magnetic measurements recorded at 5 and 300 K in an applied magnetic field of 50,000 Oe showed the magnetic properties in the antiferromagnetic and canted ferromagnetic states. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in 200 Oe and the transformation characteristic temperatures were shifted to lower values.

scholarly journals YBa2Cu3O7 films grown onto SrTiO3 and YSZ substrates by chemical solution deposition of trifluoroacetates

2021 ◽  
Author(s):  
A. Bustamante Domínguez ◽  
L. De Los Santos Valladares ◽  
H. Sanchez Cornejo ◽  
A. M. Osorio-Anaya ◽  
J. Flores Santibañez ◽  
...  
Keyword(s):  
Chemical Solution Deposition ◽  
Magnetic Measurements ◽  
Hole Concentration ◽  
Gaussian Function ◽  
Zero Field ◽  
Chemical Solution ◽  
Secondary Phases ◽  
Solution Deposition ◽  
Rocking Curve ◽  
Field Cooling

AbstractWe report the preparation and characterization of YBa2Cu3O7 (YBCO) films grown onto SrTiO3 and YSZ substrates by the trifluoroacetates chemical solution deposition method and following sintering with oxygen atmosphere at 860 °C. The X-ray diffraction (XRD) reveals (00ℓ) – oriented crystallites indicating epitaxial growth of the films in the c-direction. Despite granular morphology and the presence of Y2BaCuO5 and CuO as minor secondary phases, the technique shows the successful formation of the superconducting YBCO and preventing the formation of the unwanted BaCO3 phase. Rocking curve measurements of the (005) reflection for the YBCO/SrTiO3 was fitted with one Gaussian function with full width at the half maximum (FWHM) of 0.44° confirming that it consists of YBCO crystallites with different texture. For the sample grown on YSZ, the rocking curve was fitted with two Gaussian functions, one corresponding to the YBCO layer (FWHM = 0.4°) and another to the substrate (FWHM = 0.3°). The magnetic measurements taken in zero field cooling and field cooling modes confirm the formation of the superconducting YBCO with critical temperatures (TC) 91.8 and 85.7 K for the samples grown onto YSZ and SrTiO3, respectively. The critical current density (JC) curves indirectly calculated by using the Bean´s model from the M(T) loops were JC ~ 109 A/cm2 for the sample deposited onto YSZ and JC ~ 107A/cm2 for the YBCO deposited onto SrTiO3. Overall, the difference in TC and JC values between both samples could be related to their difference in oxygen content, porosity, hole concentration per Cu ion and the presence of secondary phases.

scholarly journals Structural and Magnetic Characterization of Polyaniline Composite Films

2008 ◽  
Vol 570 ◽  
pp. 138-143
Author(s):  
Juan C. Aphesteguy ◽  
Silvia E. Jacobo ◽  
Ricardo López Antón ◽  
G.V. Kurlyandskaya
Keyword(s):  
Electron Microscopy ◽  
Magnetic Measurements ◽  
Composite Films ◽  
Hysteresis Loops ◽  
Zero Field ◽  
Novel Approach ◽  
Transmission Electron ◽  
Temperature Dependences ◽  
Composition Structure ◽  
Field Cooling

In this work a novel approach for the preparation of Fe3O4/PANI (polyaniline) thin film composite containing magnetic nanoparticles is presented. Magnetite (Fe3O4) nanoparticles have been coated by PANI and the PANI chains have been doped by 10-camphorsulfonic acid (CSA). The doped composite is soluble in common organic solvents. Thin films of composites of polyaniline (PANI) were casted from m-cresol. Several characterization techniques were employed in order to determine composition, structure and magnetic properties of the nanocomposite film (Xray diffraction, transmission electron microscopy, TEM, Scanning electron microscopy, SEM, and optical microscopy). The magnetization data were obtained from M(H) hysteresis loops and zero field cooling – field cooling, ZFC-FC. Magnetic measurements evidence a ferromagnetic behaviour of the obtained composite, at room temperature with saturation magnetization of about 3.4 emu/g and coercivity of 42 Oe. The temperature dependences of the conductivity of the films follows the         = − 1 / 2 ( ) exp T T To o σ σ law, which has been explained within the framework of the onedimensional variable-range-hoping (1D-VRH) model. Application of 1T magnetic field increases the resistivity of the film and the temperature slope dependence.

Magnetic Properties of the Gd1-xTbxNi3 Intermetallic Compounds

2011 ◽  
Vol 170 ◽  
pp. 109-113 ◽  
Author(s):  
Anna Bajorek ◽  
Grażyna Chełkowska ◽  
Artur Chrobak ◽  
Marzena Kwiecień-Grudziecka
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Curie Temperature ◽  
Saturation Magnetization ◽  
Intermetallic Compounds ◽  
Applied Magnetic Field ◽  
Magnetic Measurements ◽  
Zero Field ◽  
Zero Field Cooling ◽  
Field Cooling

The paper presents selected magnetic properties of the Gd1-xTbxNi3 intermetallic compounds. Based on the wide-ranging SQUID magnetometer (Quantum Design MPMS, temperature from 1.9K to 300K and magnetic field up to 7T) series of different magnetic measurements were carried out. In studied system the saturation magnetization and the Curie temperature strongly depends of Tb concentration. Moreover, the so-called field cooling - zero field cooling (FC-ZFC) curves reveal a dependence of M(T) on the applied magnetic field. The thermomagnetic curves indicate interesting behaviour which is typical for terbium compounds and can be ascribed to the interaction between different aligned magnetic subblattices.

Nanocrystalline Nickel Ferrite, NiFe2O4:  Mechanosynthesis, Nonequilibrium Cation Distribution, Canted Spin Arrangement, and Magnetic Behavior

2007 ◽  
Vol 111 (13) ◽  
pp. 5026-5033 ◽  
Author(s):  
Vladimir Šepelák ◽  
Ingo Bergmann ◽  
Armin Feldhoff ◽  
Paul Heitjans ◽  
Frank Krumeich ◽  
...  
Keyword(s):  
Cation Distribution ◽  
Nickel Ferrite ◽  
Magnetic Behavior ◽  
Nanocrystalline Nickel ◽  
Canted Spin ◽  
Spin Arrangement

scholarly journals Critical Current and Pinning Features of a CaKFe4As4 Polycrystalline Sample

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6611
Author(s):  
Armando Galluzzi ◽  
Antonio Leo ◽  
Andrea Masi ◽  
Francesca Varsano ◽  
Angela Nigro ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Hysteresis Loops ◽  
Magnetic Behavior ◽  
Polycrystalline Sample ◽  
Critical Parameters ◽  
Zero Field ◽  
Critical Current Density Jc ◽  
Field Cooling

We analyze the magnetic behavior of a CaKFe4As4 polycrystalline sample fabricated by a mechanochemically assisted synthesis route. By means of DC magnetization (M) measurements as a function of the temperature (T) and DC magnetic field (H) we study its critical parameters and pinning features. The critical temperature Tc has been evaluated by M(T) curves performed in Zero Field Cooling-Field Cooling conditions. These curves show the presence of a little magnetic background for temperatures above Tc, as also confirmed by the hysteresis loops M(H). Starting from the M(H) curves, the critical current density Jc of the sample has been calculated as a function of the field at different temperatures in the framework of the Bean critical state model. The Jc(H) values are in line with the ones reported in the literature for this typology of samples. By analyzing the temperature dependence of the critical current density Jc(T) at different magnetic fields, it has been found that the sample is characterized by a strong type pinning regime. This sample peculiarity can open perspectives for future improvement in the fabrication of this material.

Sign in / Sign up

Export Citation Format

Share Document