CoPt hard magnetic nanoparticle films synthesized by high temperature chemical reduction

Abstract

The synthesis of hard-magnetic CoPt nanoparticle films by hydrogen reduction of Co nitride and Pt chloride mixture is reported. Thin porous alumina films are adopted as the carrier of the initial aqueous solution and of the final reducing products of CoPt nanoparticles. It is found that chemical ordering of L1 0 -CoPt occurs above 400°C. Partial phase transformation occurs in the alumina substrate when the treatment temperature is higher than 600°C. The film coercivity increases with increasing annealing temperature and reaches a maximum value of 24.2 kOe when the reduction is carried out at 700°C for 2 h.

Laser ablation synthesis of monodispersed magnetic alloy nanoparticles

“…Similar results have been obtained with measurements for Ni . On the other hand, the coercive force was smaller than the reported value for ordered L1 0 composed of chemically synthesized CoPt alloy nanoparticles (24.2 kOe; Sui et al, 2003). This was probably due to the lack of ordering or to the slight difference in the composition.…”

“…Because of their large magnetic anisotropy, CoPt and FePt alloy nanoparticles are thought to hold great promise as candidates for the next generation of ultrahigh-density magnetic recording media (Sun et al, 2000;Yu et al, 2002;Sui et al, 2003). When these alloys are synthesized by the conventional methods of liquid phase process and sputtering, however, the size and crystal structure cannot be controlled with the precision required to obtain large magnetic anisotropy.…”

Growth and magnetism of FePt:C composites in nanoscale channels

“…[1][2][3] It is normally found that the coercivities of the FePt clusters increase when they are treated at high temperatures, which results from the high degree of chemical ordering and improved magnetocrystalline anisotropy. It is also found that aggregation of clusters occurs when they are treated at high temperature, which is not desired for nanocomposite magnets or magnetic recording media, and there is not a simple method to prevent them from aggregating.…”

“…3,4 In this study, cluster-assembled FePt:C composites were produced within the nanochannels of alumina films by combining hydrogen reduction and chemical vapor deposition ͑CVD͒. 2,5 The presence of carbon blocks the agglomeration of fine clusters when heated to high temperatures. The sizes and the morphologies of FePt clusters inside the nanochannels are studied together with their magnetic properties.…”

Magnetic nanotubes produced by hydrogen reduction

“…[1][2][3] An emerging area is the synthesis of tubular nanostructures, which was pioneered in inorganic chemistry. 4 -7 The methods used up to now, such as chemical synthesis 1 and templatedirected growth, [8][9][10] make it difficult to tune the magnetic properties of the structures. This refers, in particular, to magnetic quantities such as anisotropy and coercivity, which are important for many present and future applications in permanent magnetism, magnetic recording, and spin electronics.…”