Fabrication of ordered nanomagnet arrays with controlled magnetic alignment is an important goal in achieving high density information storage and high performance permanent magnets. For a uniaxial anisotropic nanomagnet, magnetic alignment infers
that magnetization of the magnet lies only along the “easy direction”. In ferromagnetic hysteresis behaviors, such an alignment corresponds to a hysteresis loop with high squareness, which leads to the remanent magnetization value close to the saturation one. Magnets with this magnetic behavior can have distinct magnetization
reversals and retain maximum magnetic energy for data storage and permanent magnetic applications.

In searching for shape-controlled synthesis of FePt nanoparticles, we found that simultaneous decomposition of Fe(CO)5 and reduction of Pt(acac)2 without polyol as a reducing agent yielded FePt nanoparticles with sizes tunable from 3 to 9 nm. Our
further synthetic studies revealed that, by controlling the addition sequence of the stabilizers (oleic acid and oleylamine) and Fe/Pt ratio in the precursors, FePt nanocubes could be prepared at relatively low temperature (205 °C).

The work demonstrates that shapecontrolled synthesis and self-assembly can offer a simple solution to fabrication of magnetically aligned FePt nanocrystal arrays that
are promising for single nanoparticle recording and for high performance exchange-spring nanocomposite magnet applications.

For the FePt nanocubes of 7 nm in this paper, the coercivity of the nanocube assembley is about 20 kOe. Does anyone what kind of technology (like MFM) can detect the individual magnetic moment signal? So far as I know, current magnetic R/W head in hard disk cannot reach such resolution.