In situ magnetic field alignment of directly ordered L1 FePt nanoparticles

Abstract

Gas-phase prepared directly ordered FePt nanoparticles were shown to align with in situ magnetic fields. As shown by magnetic and x-ray diffraction data, a 3800Oe perpendicular field switched L10 FePt particles with a mean size of 6nm from in-plane arrangement in as-deposited state to out-of-plane orientation. A 5000Oe in-plane field successfully defined nanoparticles with in-plane texture. These results demonstrated the feasibility of preparing nanoparticle-based magnetic recording media and exchange-spring-type permanent magnets with desired magnetic orientation control. Only involving thermal fluctuation as the obstacle, this approach makes an ideal subject for theoretical understanding and further optimization.

Prospects for nanoparticle-based permanent magnets

“…The cluster-deposition method is capable of producing directly ordered permanent-magnet nanoparticles by aligning their easy axes through applications of a magnetic field using a set of permanent magnets prior to deposition on substrates [18,30,31,[41][42][43]. The alignment process causes a significant increase in H c and M r /M s in the easy-axis direction compared with those in the hardaxis direction as shown in the case of magnetically aligned SmCo 5 nanoparticles (Figure 4b) [41].…”

One-step fabrication of L1 FePt nanocubes and rods by cluster beam deposition

“…11,12 Although particles with the low ordering parameter 0.5 have the cubic shape, the possibility of particles becoming octahedral by improving the ordering cannot be excluded. On the other hand, at very high sputtering power it is very unlikely to expect the typical shape formations due to the non-equilibrium conditions.…”

Novel structures and physics of nanomagnets (invited)

“…15,16 Nanomagnetic assemblies produced using wet-chemical, conventional thin-film, and gas-aggregation-type clusterdeposition methods have shown uniform distribution of particle sizes with well-controlled compositions and interfaces. 1,[17][18][19][20][21][22][23][24][25] In particular, the non-equilibrium clusterdeposition method has produced directly nanoparticles of metastable and traditional magnetic phases with a high degree of crystalline ordering. 5,[21][22][23][24][25] In addition, during the crystallization process, the modified thermodynamic and kinetic factors lead to new crystal structures in nanoclusters that are not possible in the case of bulk alloys, 6,26,27 and also favor specialized nanostructures such as core-shell and composite nanoclusters with interesting magnetic properties.…”

“…1,[17][18][19][20][21][22][23][24][25] In particular, the non-equilibrium clusterdeposition method has produced directly nanoparticles of metastable and traditional magnetic phases with a high degree of crystalline ordering. 5,[21][22][23][24][25] In addition, during the crystallization process, the modified thermodynamic and kinetic factors lead to new crystal structures in nanoclusters that are not possible in the case of bulk alloys, 6,26,27 and also favor specialized nanostructures such as core-shell and composite nanoclusters with interesting magnetic properties. 6,28 It is important to note that the sintering associated with the annealing process is avoidable in the case of the clusterdeposition method, and thus nanoclusters can be assembled with atoms forming a second phase with properties that complement those of the nanocluster phase.…”