FePt alloy

The ability to synthesize lattices of nanociystals have led to explorations of their collective physical properties. Thus, it is observed in the case, of Co nanociystals (5.8 nm) that, accompanying lattice formation, the blocking temperature increases. 421 FePt alloy nanocrystals yield ferromagnetic assemblies for which the coerrivity is tunable by controlling the parameters such as Fe Pt ratio and the particle size.1431 The evolution of collective electronic states in CdSe nanocrystals have been followed by optical spectroscopic methods. Compared with isolated nanocrystals, those in the lattice exhibited... 

Chen W, BGm J, Sun S, Chen S (2007) Composition effects of FePt alloy nanoparticles on the electro-oxidatitm of formic acid. Langmuir 23 11303-11310... 

Depending on the type of the alloy, different models can be used to calculate the activity coefficient. For electrodeposited CoPt and FePt alloys which show strong negative departure from ideality,an asymmetric regular solution model is used to define XB (B = Fe or Co) ... 

N. Moghimi, K.T. Leung, FePt alloy nanoparticles for biosensing Enhancement of vitamin C sensor performance and selectivity by nanoalloying. Anal. Chem. 85 (2013) 5974-5980. 

PdPt [96,111], CuPt [112], PdRh [113], FeRu [114], FePt [114], FeNi [115], CuNi [116], BiNi [117] nanoparticle alloys or cluster-in-cluster structures by simultaneous reduction were reported, as summarized in Table la and b. 

The TEM image in the figure shows particles less than 10 nm in size corresponding to a coercivity of 7 kOe. The values of coercivity here do not approach those expected for the anisotropy of pure SmCo5 phase due to alloying with the tungsten. When multilayered with Cr the coercivity reaches 30 kOe for similar particle sizes [11]. These high anisotropy materials like FePt and SmCos are very sensitive to composition as will be discussed in the next section. 

The current-write anisotropy-field cut-off is believed to be about HKmax = 20-30 kOe for perpendicular recording, which requires most advanced writer head technology and includes enhancements such as tilted [15, 16] and/or recently proposed exchange-coupled composite media [54, 55], Hence, most of the materials listed in Table 2 are excluded from perpendicular media applications. Co-rich Co-Pt based alloys and Co/Pd type multilayers look promising from the perspective of near term extensions to higher write coercivities. Future HAMR media candidates are mainly Co/Pt based multilayers (Dp 6.1-8.3 nm) (entry level) and ultimately FePt-Zl0-compounds (Dp 2.4-4.4 nm). 

Thin metalhc fihns play an important role in diverse fields of applications, with special emphasis on micro- and nanoelectronics for which the metals Al, Cu, Ag, Au, Ti and W are essential Additional fields of commercial interests are electrodes as well as reflective, corrosion-resistant, oxidation-resistant and abrasion-resistant coatings . Noble metals (periods 5 and 6 of groups 8-11 of the periodic table of the elements) are of special interest due to their manifold application in heterogeneous catalysis. Other metals used in specialized industrial applications or as components of more complex materials such as metal alloys are Ni, Pd, Pt, Ag and Au. For example, FePt-based nanostructured materials are excellent candidates for future high-density magnetic recording media . ... 

These magnetic properties are easily obtainable with presently well-known high materials such as FePt [32] and Co-Pt alloy [33] as described in the previous section. Conseqnently, it is very much possible to design a medium for a density of 1 Tera bits/inch in terms of thermal stability, recording feasibility and applicable materials withont any corrosion problems. 

Finally, it may be noted that alloying Fe and Co with precious metals leads to the phases FePt, CoPt, and FePd with an LIq structure, which is an ordered f.c.c. structure with tetragonal distortion (see Fig. 1). These phases have been of importance for applications as permanent magnetic materials, and in particular CoPt, which is used in the only partially ordered state, excels because of isotropy, ductility, easy machinability and resistance to corrosion and high temperatures (Jellinghaus, 1936 Kouvel, 1967 Chin and Wernick,... 

An interesting approach to synthesize metal alloy nanocrystals is the use of simultaneous salt reduction and thermal decomposition processes. Sun et al. [18] reported on the synthesis of iron-platinum (FePt) nanoparticles through the reduction of platinum acetylacetonate by a diol, and decomposition of iron pentacarbonyl (Fe(CO)5) in the presence of a surfactant mixture (oleic acid and oleyl amine). On the basis of a similar approach, Chen and Nikles [217] synthesized ternary alloy nanoparticles (FC cCo3,Ptioo x-y), using a simultaneous reduction of acetylacetonate and platinum acetylacetonate and thermal decomposition of Fe(CO)5 and obtaining an average particle diameter of 3.5 nm and narrow particle size distribution. 

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