Alloy nanoparticles, method of producing the same, and magnetic recording medium using alloy nanoparticles

A method of producing alloy nanoparticles having a predetermined average grain diameter, comprising the steps of:

• adding a metallic salt, a reducing agent, a controlled amount of stabilizing ligand to produce the predetermined average diameter, and an organic iron complex to an organic solvent selected from the group consisting of 2-20C hydrocarbon, alcohol, ether, and ester in an inert gas atmosphere to obtain a reaction liquid;
• and
• stirring said reaction liquid while heating said liquid to a predetermined temperature in the range of 220-259° C.,
• wherein the grain diameter of said alloy nanoparticles is controlled by the amount of said stabilizing ligand.

A magnetic recording medium comprising:

• a substrate;
• a nanoparticle magnetic layer containing FePt alloy nanoparticles which are disposed at substantially uniform intervals on said substrate, and have an average diameter of 2 to 10 nm, and a carbon phase filling the voids between said FePt alloy nanoparticles;
• and
• a protective film formed on said nanoparticle magnetic layer, wherein the proportion of the number of carbon atoms contained in said carbon phase based on the sum of the number of metallic atoms constituting said FePt alloy nanoparticles and the number of said carbon atoms is in the range of from 50 at %, inclusive, to 85 at %, exclusive.

A method of manufacturing a magnetic recording medium, comprising the steps of:

• dispersing FePt alloy nanoparticles and an organic mixture containing a carboxylic acid and an amine in a solvent selected from the group consisting of hexane, heptane, and octane, to obtain a coating liquid;
• applying said coating liquid to a substrate;
• drying said coating liquid to form, on said substrate, a magnetic nanoparticle layer comprised of said FePt alloy nanoparticles and said organic mixture filling the voids between said FePt alloy nanoparticles;
• and
• annealing said magnetic nanoparticle layer.