Non-symmetric superparamagnetic clusters in the relaxor manganites Sr2−xBixMnTiO6 (0 ≤ x ≤ 0.75)

2012 ◽  
Vol 22 (23) ◽  
pp. 11826 ◽  
Author(s):  
Inmaculada Álvarez-Serrano ◽  
M. Luisa López ◽  
Fausto Rubio ◽  
Mar García-Hernández ◽  
Gabriel J. Cuello ◽  
...  
Keyword(s):  
Superparamagnetic Clusters

scholarly journals Magnetometric Study Of ZnO/CoO Nanocomposites

2018 ◽  
Vol 57 (1) ◽  
pp. 11-25 ◽  
Author(s):  
J. Typek ◽  
N. Guskos ◽  
G. Zolnierkiewicz ◽  
D. Sibera ◽  
U. Narkiewicz
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Applied Pressure ◽  
Transition Metal Ions ◽  
Short Review ◽  
Magnetic Interactions ◽  
Magnetic Characteristics ◽  
Heterogeneous Distribution ◽  
Magnetic Systems ◽  
Superparamagnetic Clusters

Abstract ZnO nanoparticles doped with transition metal ions are intensively studied nanomaterials, due to their charges and the spins of electrons that provides new magnetic, optical and transport properties. They find a vast range of applications, ranging from optoelectronics to spintronics. In this context especially important is the room temperature ferromagnetism observed for ZnO doped nanomaterials, although this phenomenon is still a controversial and open topic in material science, mostly due to low reproducibility of results from samples prepared by different techniques. In the first part of this article a short review of papers using magnetometric methods to determine the magnetic characteristics of Co-doped ZnO nanomaterials is presented. Different models introduced to explain room temperature ferromagnetism (carrier mediated ferromagnetism, Co2+-oxygen vacancy pairs, blocked superparamagnetic clusters, Co2+-Zn interstitial pairs, heterogeneous distribution of magnetic ions) are examined and discussed. In the second part, magnetisation study of a new series of nCoO/(1-n)ZnO nanocomposites synthesized by hydrothermal method under higher than previously applied pressure will be described. The obtained experimental results will be analysed and information on magnetic systems responsible for the observed characteristics and the involved magnetic interactions will be deduced.

MAGNETISM IN TRANSITION-METAL CLUSTERS FROM THE ATOM TO THE BULK

1996 ◽  
Vol 03 (01) ◽  
pp. 429-434 ◽  
Author(s):  
I.M.L. BILLAS ◽  
A. CHÂTELAIN ◽  
W.A. de HEER
Keyword(s):  
Molecular Beam ◽  
Magnetic Moments ◽  
Beam Deflection ◽  
Transition Metal Clusters ◽  
Iron Cluster ◽  
Iron Cobalt ◽  
Nickel Clusters ◽  
Magnetic Shell ◽  
Superparamagnetic Clusters ◽  
Cobalt And Nickel

Molecular beam deflection measurements of small iron, cobalt, and nickel clusters show how magnetism develops as the cluster size is increased from several tens to several hundreds of atoms for temperatures from 80 and 1000 K. Cluster magnetization is found to be superparamagnetic for rotationally warm clusters, where it follows the Langevin function. The magnetization of rotationally cold clusters is anomalous: it is strongly reduced and nonlinear with the applied field. For superparamagnetic clusters, the magnetic moments can be determined from the magnetization. We find that ferromagnetism occurs even for the smallest sizes: for clusters with less than about 30 atoms the magnetic moments are atom-like and as the size is increased up to 700 atoms they approach the bulk limit, with oscillations probably caused by surface-induced spin-density waves. The trends are explained in a magnetic shell model. The magnetic properties of iron cluster show anomalies, suggesting that a high moment to low moment crystallographic phase transition in Fe clusters occurs at relatively low temperatures.

scholarly journals Электрофизические свойства поликристаллических пленок BiFe-=SUB=-0.95-=/SUB=-Co-=SUB=-0.05-=/SUB=-O-=SUB=-3-=/SUB=-

2021 ◽  
Vol 63 (6) ◽  
pp. 721
Author(s):  
О.Б. Романова ◽  
В.В. Кретинин ◽  
С.С. Аплеснин ◽  
М.Н. Ситников ◽  
Л.В. Удод ◽  
...  
Keyword(s):  
Thin Film ◽  
Phase Transition ◽  
Impedance Spectrum ◽  
Spin Fluctuations ◽  
Kinetic Properties ◽  
Surface Phase ◽  
Cobalt Ions ◽  
Hall Effect Measurements ◽  
Superparamagnetic Clusters ◽  
Electronic Doping

Semiconductor BiFe0.95Co0.05O3 thin-film compounds were obtained by a flare technique. The surface morphology of the films and the effect of electronic doping by replacing trivalent iron with cobalt ions on the structural, optical, magnetic, and kinetic properties in the temperature range 77-600 K in magnetic fields up to 12 kOe are studied. The existence of two relaxation channels in the impedance spectrum at frequencies of 0.1–1000 kHz has been established. The negative magnetoresistance in the anomalous magnetization region and the maximum magnetoimpedance in the vicinity of the surface phase transition has been found. Using the Hall effect measurements, carrier types prevailing in the magnetoresistance and magnetoimpedance effects has been found. The magnetization anomalies are explained using the model of superparamagnetic clusters and the magnetoresistance is attributed to the scattering of carriers by the spin fluctuations.

Mössbauer study of the Ni–Zn ferrite system

1970 ◽  
Vol 48 (4) ◽  
pp. 381-396 ◽  
Author(s):  
J. M. Daniels ◽  
A. Rosencwaig
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Full Range ◽  
Zinc Content ◽  
Zero Magnetic Field ◽  
Nickel Zinc ◽  
Zn Ferrite ◽  
Superparamagnetic Clusters ◽  
Ferrite System ◽  
Nuclear Magnetic

Mössbauer spectra of 57Fe in the nickel–zinc ferrite system (ZnO)x(NiO)1−xFe2O3 have been obtained, at room temperature and at 77 °K, in zero magnetic field and also in a longitudinal magnetic field of 13.5 kG, covering the full range of zinc content. The dependence of the isomer shifts, line widths, quadrupole interactions, and nuclear magnetic fields of 57Fe3+ ions in both tetrahedral and octahedral sites has been determined. The principal results of this study are (a) the confirmation of the determination of the nuclear magnetic fields by Abe et al. using NMR, and the extension of these measurements to higher zinc concentrations, (b) an indication that the hypotheses of paramagnetic centers, proposed by Gilleo, and superparamagnetic clusters, proposed by Ishikawa, are not applicable to the nickel–zinc ferrites, (c) evidence of canted spin structures, first proposed by Yafet and Kittel, (d) various effects of chemical disorder in the nickel-zinc ferrites, and (e) an observation of the effect on the Mössbauer spectrum of relaxation in a magnetically ordered iron system.

Numerical analysis of superparamagnetic clusters distribution

2011 ◽  
Vol 208 (11) ◽  
pp. 2692-2698 ◽  
Author(s):  
A. Chrobak ◽  
G. Haneczok ◽  
G. Chełkowska ◽  
A. Kassiba ◽  
G. Ziółkowski
Keyword(s):  
Numerical Analysis ◽  
Superparamagnetic Clusters
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