TEM image of the γ-Fe2O3 ferrofluid. Inset: Distribution of particle diameters determined from the analysis of TEM data.
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).
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.
Hysteresis loop of the RDM (○) and TXT (•) samples at . The area increases after the protocol 2.
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
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.
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.
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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