Abstract
During the past decade, CoFe2O4 (hard)/Co Fe alloy (soft) magnetic nanocomposites have been routinely prepared by partial reduction of CoFe2O4 nanoparticles. Monoxide (i.e., FeO or CoO) has often been detected as a byproduct of the reduction, although it remains unclear whether the formation of this phase occurs during the reduction itself or at a later stage. Here, a novel reaction cell was designed to monitor the reduction in situ using synchrotron powder X-ray diffraction (PXRD). Sequential Rietveld refinements of the in situ data yielded time-resolved information on the sample composition and confirmed that the monoxide is generated as an intermediate phase. The macroscopic magnetic properties of samples at different reduction stages were measured by means of vibrating sample magnetometry (VSM), revealing a magnetic softening with increasing soft phase content, which was too pronounced to be exclusively explained by the introduction of soft material in the system. The elemental compositions of the constituent phases were obtained from joint Rietveld refinements of ex situ high resolution PXRD and neutron powder diffraction (NPD) data. It was found that the alloy has a tendency to emerge in a Co-rich form, inducing a Co deficiency on the remaining spinel phase, which can explain the early softening of the magnetic material.
| Original language | English |
|---|---|
| Journal | ACS Applied Nano Materials |
| Volume | 1 |
| Issue number | 7 |
| Pages (from-to) | 3693-3704 |
| Number of pages | 23 |
| ISSN | 2574-0970 |
| DOIs | |
| Publication status | Published - 2018 |
Keywords
- Nanocomposite
- Ferrite
- Permanent magnet
- Exchange-coupling
- In Situ
- Neutron powder diffraction
- Elemental composition
- Rietvield refinement
Cite this
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Approaching Ferrite-Based Exchange-Coupled Nanocomposites as Permanent Magnets. / Granados-Miralles, Cecilia; Saura-Muzquiz, Matilde; Andersen, Henrik L.; Quesada, Adrian; Ahlburg, Jakob V.; Dippel, Ann-Christin; Canevet, Emmanuel; Christensen, Mogens.
In: ACS Applied Nano Materials , Vol. 1, No. 7, 2018, p. 3693-3704.Research output: Contribution to journal › Journal article › Research › peer-review
TY - JOUR
T1 - Approaching Ferrite-Based Exchange-Coupled Nanocomposites as Permanent Magnets
AU - Granados-Miralles, Cecilia
AU - Saura-Muzquiz, Matilde
AU - Andersen, Henrik L.
AU - Quesada, Adrian
AU - Ahlburg, Jakob V.
AU - Dippel, Ann-Christin
AU - Canevet, Emmanuel
AU - Christensen, Mogens
PY - 2018
Y1 - 2018
N2 - During the past decade, CoFe2O4 (hard)/Co Fe alloy (soft) magnetic nanocomposites have been routinely prepared by partial reduction of CoFe2O4 nanoparticles. Monoxide (i.e., FeO or CoO) has often been detected as a byproduct of the reduction, although it remains unclear whether the formation of this phase occurs during the reduction itself or at a later stage. Here, a novel reaction cell was designed to monitor the reduction in situ using synchrotron powder X-ray diffraction (PXRD). Sequential Rietveld refinements of the in situ data yielded time-resolved information on the sample composition and confirmed that the monoxide is generated as an intermediate phase. The macroscopic magnetic properties of samples at different reduction stages were measured by means of vibrating sample magnetometry (VSM), revealing a magnetic softening with increasing soft phase content, which was too pronounced to be exclusively explained by the introduction of soft material in the system. The elemental compositions of the constituent phases were obtained from joint Rietveld refinements of ex situ high resolution PXRD and neutron powder diffraction (NPD) data. It was found that the alloy has a tendency to emerge in a Co-rich form, inducing a Co deficiency on the remaining spinel phase, which can explain the early softening of the magnetic material.
AB - During the past decade, CoFe2O4 (hard)/Co Fe alloy (soft) magnetic nanocomposites have been routinely prepared by partial reduction of CoFe2O4 nanoparticles. Monoxide (i.e., FeO or CoO) has often been detected as a byproduct of the reduction, although it remains unclear whether the formation of this phase occurs during the reduction itself or at a later stage. Here, a novel reaction cell was designed to monitor the reduction in situ using synchrotron powder X-ray diffraction (PXRD). Sequential Rietveld refinements of the in situ data yielded time-resolved information on the sample composition and confirmed that the monoxide is generated as an intermediate phase. The macroscopic magnetic properties of samples at different reduction stages were measured by means of vibrating sample magnetometry (VSM), revealing a magnetic softening with increasing soft phase content, which was too pronounced to be exclusively explained by the introduction of soft material in the system. The elemental compositions of the constituent phases were obtained from joint Rietveld refinements of ex situ high resolution PXRD and neutron powder diffraction (NPD) data. It was found that the alloy has a tendency to emerge in a Co-rich form, inducing a Co deficiency on the remaining spinel phase, which can explain the early softening of the magnetic material.
KW - Nanocomposite
KW - Ferrite
KW - Permanent magnet
KW - Exchange-coupling
KW - In Situ
KW - Neutron powder diffraction
KW - Elemental composition
KW - Rietvield refinement
U2 - 10.1021/acsanm.8b00808
DO - 10.1021/acsanm.8b00808
M3 - Journal article
VL - 1
SP - 3693
EP - 3704
JO - ACS Applied Nano Materials
JF - ACS Applied Nano Materials
SN - 2574-0970
IS - 7
ER -