CoPt magnetic nanocrystals in the A1/L1 transformation

Abstract

Roles of L10 ordering in controlling the magnetic anisotropy and coercivity of (111)-oriented CoPt ultrathin continuous layers in CoPt/AlN multilayer films

Role of the nanocrystallinity on the chemical ordering of CoxPt100−x nanocrystals synthesized by wet chemistry

“…NCs synthesized by the LLPT method with same size, but passivated also by alkylamine chains showed a huge coalescence and a chemical ordering only above 500 ºC [16]. Again, we observe the beginning of chemical ordering at lower temperature for (CoPt) Polyol than for (CoPt) LLPT independent of the composition.…”

“…Figure 2 shows Co x Pt 100-x nanoalloys obtained by the polyol process with two different compositions as determined by the EDS analysis ( Figure 2G images show well-dispersed spherical NCs (Figure 2A and 2B). It can be seen that the NCs are homogeneous in size, shape and electronic contrast indicating the absence of segregation or core-shell structure [16]. A slight decrease in the average size while preserving the same polydispersity is observed for different composition of the CoPt, i.e.…”

“…A thermal annealing is required to induce ordering toward L1 0 or L1 2 structure, depending on the composition [15]. For supported nanoparticles, the thermal assistances at high temperature (> 300°C) can lead to coalescence and sintering effects, which increase the size, modify the shape and destroy their organization [15,16]. Indeed, the driving force for coalescence and the change of shape is the minimization of surface energy by elimination of interfaces and appearance of grain boundaries and defects [15].…”

Protective Effect of Polyoxometalates in {Mo132}/Maghemite Binary Superlattices Under Annealing

“…Beyond obtaining a binary system with specific properties, one issue can be crucial, specifically in the magnetism and transport fields: the annealing of the binary assembly. Indeed, an annealing can be necessary to change the phase of the nanocrystals and form hard magnetic phases (Zeng et al, 2002; Lisiecki et al, 2007; Parker et al, 2007; Demortière and Petit, 2011; Dong et al, 2011), or to desorb the organic capping around the nano-objects that can be an obstacle to transport measurements (Chen et al, 2013). As the surrounding ligand has a key role in the formation of the binary superlattices (Boles and Talapin, 2015; Wei et al, 2015; Huang et al, 2016; Travesset, 2017), the ligand desorption has to be done after the formation of the binary assembly.…”

“…As the surrounding ligand has a key role in the formation of the binary superlattices (Boles and Talapin, 2015; Wei et al, 2015; Huang et al, 2016; Travesset, 2017), the ligand desorption has to be done after the formation of the binary assembly. However, due to the needed high temperatures, the annealing procedure can induce coalescence phenomena leading to an increase in the size of the NCs, a modification of the shape and a change in the organization (Klemmer et al, 2003; Alloyeau et al, 2010; Demortière and Petit, 2011). In this context, one of the main challenges is to be able to anneal the nanostructured film while preventing from the aggregation of the nano-objects and keeping the periodicity in the binary system, both for addressing individual magnetic objects and for controlling the charge transport (Dong et al, 2011; Altantzis et al, 2016).…”