Liquid phase syntheses mainly yield nanoparticles with
compact
shapes, such as spheres or cubes. However, controlling not only the
size but also the shape of magnetic nanoparticles would enable a fine-tuning
of their intrinsic properties, due to the shape anisotropy induced
by long-range dipolar interactions. We report here a fairly simple
approach based on the reduction of an amidinate complex in the presence
of a mixture of long-chains acid and amine to yield ferromagnetic
Ni nanoparticles. The formation of stable Ni complexes could be promoted in situ by increasing the acid concentration, thus allowing
tuning of the final particle size. While amine could be used as a
soft reducing agent, dihydrogen was essential to promote anisotropic
shapes. Electron holography combined with micromagnetic simulations
showed that the resulting shape anisotropy could impose complex magnetic
configurations within planar tetrapods. Regarding the heating efficiency,
which directly scales with the magnetic hysteresis loop area, maxima
of 100W·g–1 were found for nanoplates and nanorods,
opening promising perspectives for magnetically induced catalysis.
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