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Texture-induced magnetic interactions in ferrofluids
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10.1063/1.4709725
/content/aip/journal/jap/111/9/10.1063/1.4709725
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/9/10.1063/1.4709725
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

TEM image of the γ-Fe2O3 ferrofluid. Inset: Distribution of particle diameters determined from the analysis of TEM data.

Image of FIG. 2.
FIG. 2.

SAXS intensity profiles measured at room temperature. Solid symbols represent the scattering profile in the presence of a magnetic field . The SAXS intensity in the absence of any magnetic field is also shown (open symbols).

Image of FIG. 3.
FIG. 3.

Experimental protocols employed to control the magnetic texture. Protocol 1: The sample is cooled down from room temperature to 1.8 K in zero magnetic field; the easy axes of the nanoparticles stay oriented at random. Protocol 2: The sample is frozen to 110 K under a magnetic field of 50 kOe; it is subsequently cooled to 1.8 K (crossing T B) in zero field. The angle ψ that the easy axes made with the measuring field ranges from zero to ψmax, which is zero for a perfect alignment and π/2 for randomly oriented axes.

Image of FIG. 4.
FIG. 4.

Hysteresis loop of the RDM (○) and TXT (•) samples at . The area increases after the protocol 2.

Image of FIG. 5.
FIG. 5.

AC susceptibility curves measured at different frequencies: Solid symbols are for the TXT; open symbols are for the non textured sample (RDM). Above the melting point of the solvent the susceptibility of sample TXT agrees with that of sample RDM. Inset: Magnification of the low temperature region

Image of FIG. 6.
FIG. 6.

Reciprocal ac susceptibilities of the TXT (solid symbols) and the RDM (open symbols) samples. The solid lines are Curie-Weiss fits of data measured in the temperature region , in which the susceptibilities of both samples attain their thermal equilibrium values.

Image of FIG. 7.
FIG. 7.

Arrhenius plot of the magnetic relaxation time of RDM (○) and TXT samples (•). The values of the effective activation energies U eff and the attempt times τ0 obtained for each sample from the Arrhenius fits (solid lines) are given.

Image of FIG. 8.
FIG. 8.

χ″ as a function of the scaling variable , with and for RDM and TXT samples, respectively. The size distribution determined by TEM is also included for comparison to the distributions obtained from χ″. Inset: χ″ scaled to the maxima.

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/content/aip/journal/jap/111/9/10.1063/1.4709725
2012-05-04
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Texture-induced magnetic interactions in ferrofluids
http://aip.metastore.ingenta.com/content/aip/journal/jap/111/9/10.1063/1.4709725
10.1063/1.4709725
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