Magnetic correlations in non-percolated Co-SiO2 granular films

Sandra Sankar; A. E. Berkowitz; D. Dender; J. A. Borchers; R. W. Erwin; S. R. Kline; David Smith

doi:10.1016/S0304-8853(00)00391-7

Magnetic correlations in non-percolated Co-SiO₂ granular films

Sandra Sankar, A. E. Berkowitz, D. Dender, J. A. Borchers, R. W. Erwin, S. R. Kline, David Smith

Research output: Contribution to journal › Conference article › peer-review

76 Scopus citations

Abstract

The zero-field-cooled state of Co_x(SiO₂)_1-x granular films was investigated with small-angle neutron scattering, low-field AC magnetic susceptibility χ(T), and magnetoresistance measurements. Films with metallic volume fraction x = 0.41, which consist of 40 angstroms isolated particles that are superparamagnetic at room temperature, show an ordered magnetic state below 150 K consisting of 550 angstroms correlated regions that are aligned antiferromagnetically. The ordering is attributed to dipolar interactions. The temperature for the onset of correlated behavior, obtained from SANS (faster than 10_-10 s), coincides with the frequency-independent maximum of χ′(T) for frequencies ranging from 0.1 to 1000 Hz. Furthermore, consistent with ferromagnetic correlations, the ZFC resistance is not the maximum resistance. Films with x = 0.32 exhibit evidence of magnetic interactions but no extended magnetic correlation - the magnetic correlation length corresponds to the particle size.

Original language	English (US)
Pages (from-to)	1-9
Number of pages	9
Journal	Journal of Magnetism and Magnetic Materials
Volume	221
Issue number	1-2
DOIs	https://doi.org/10.1016/S0304-8853(00)00391-7
State	Published - Nov 2000
Event	3rd Euroconference on Magnetic Properties of Fine Particles and their Relevance to Materials Science - Barceolona, Spain Duration: Oct 19 1999 → Oct 22 1999

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

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10.1016/S0304-8853(00)00391-7

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title = "Magnetic correlations in non-percolated Co-SiO2 granular films",

abstract = "The zero-field-cooled state of Cox(SiO2)1-x granular films was investigated with small-angle neutron scattering, low-field AC magnetic susceptibility χ(T), and magnetoresistance measurements. Films with metallic volume fraction x = 0.41, which consist of 40 angstroms isolated particles that are superparamagnetic at room temperature, show an ordered magnetic state below 150 K consisting of 550 angstroms correlated regions that are aligned antiferromagnetically. The ordering is attributed to dipolar interactions. The temperature for the onset of correlated behavior, obtained from SANS (faster than 10-10 s), coincides with the frequency-independent maximum of χ′(T) for frequencies ranging from 0.1 to 1000 Hz. Furthermore, consistent with ferromagnetic correlations, the ZFC resistance is not the maximum resistance. Films with x = 0.32 exhibit evidence of magnetic interactions but no extended magnetic correlation - the magnetic correlation length corresponds to the particle size.",

author = "Sandra Sankar and Berkowitz, {A. E.} and D. Dender and Borchers, {J. A.} and Erwin, {R. W.} and Kline, {S. R.} and David Smith",

year = "2000",

month = nov,

doi = "10.1016/S0304-8853(00)00391-7",

language = "English (US)",

volume = "221",

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journal = "Journal of Magnetism and Magnetic Materials",

issn = "0304-8853",

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note = "3rd Euroconference on Magnetic Properties of Fine Particles and their Relevance to Materials Science ; Conference date: 19-10-1999 Through 22-10-1999",

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TY - JOUR

T1 - Magnetic correlations in non-percolated Co-SiO2 granular films

AU - Sankar, Sandra

AU - Berkowitz, A. E.

AU - Dender, D.

AU - Borchers, J. A.

AU - Erwin, R. W.

AU - Kline, S. R.

AU - Smith, David

PY - 2000/11

Y1 - 2000/11

N2 - The zero-field-cooled state of Cox(SiO2)1-x granular films was investigated with small-angle neutron scattering, low-field AC magnetic susceptibility χ(T), and magnetoresistance measurements. Films with metallic volume fraction x = 0.41, which consist of 40 angstroms isolated particles that are superparamagnetic at room temperature, show an ordered magnetic state below 150 K consisting of 550 angstroms correlated regions that are aligned antiferromagnetically. The ordering is attributed to dipolar interactions. The temperature for the onset of correlated behavior, obtained from SANS (faster than 10-10 s), coincides with the frequency-independent maximum of χ′(T) for frequencies ranging from 0.1 to 1000 Hz. Furthermore, consistent with ferromagnetic correlations, the ZFC resistance is not the maximum resistance. Films with x = 0.32 exhibit evidence of magnetic interactions but no extended magnetic correlation - the magnetic correlation length corresponds to the particle size.

AB - The zero-field-cooled state of Cox(SiO2)1-x granular films was investigated with small-angle neutron scattering, low-field AC magnetic susceptibility χ(T), and magnetoresistance measurements. Films with metallic volume fraction x = 0.41, which consist of 40 angstroms isolated particles that are superparamagnetic at room temperature, show an ordered magnetic state below 150 K consisting of 550 angstroms correlated regions that are aligned antiferromagnetically. The ordering is attributed to dipolar interactions. The temperature for the onset of correlated behavior, obtained from SANS (faster than 10-10 s), coincides with the frequency-independent maximum of χ′(T) for frequencies ranging from 0.1 to 1000 Hz. Furthermore, consistent with ferromagnetic correlations, the ZFC resistance is not the maximum resistance. Films with x = 0.32 exhibit evidence of magnetic interactions but no extended magnetic correlation - the magnetic correlation length corresponds to the particle size.

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AN - SCOPUS:0034315621

SN - 0304-8853

VL - 221

SP - 1

EP - 9

JO - Journal of Magnetism and Magnetic Materials

JF - Journal of Magnetism and Magnetic Materials

IS - 1-2

T2 - 3rd Euroconference on Magnetic Properties of Fine Particles and their Relevance to Materials Science

Y2 - 19 October 1999 through 22 October 1999

ER -

Magnetic correlations in non-percolated Co-SiO₂ granular films

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