Iranian researchers have fabricated nano magnetic memories by means of hard magnetic alloy materials which could result in improvement of magnetic hard disks quality. Magnetic nanoparticles provide local and independent magnetic behavior in a two dimensional space under a variable field.
The advantage of these spaces over multilayered ones is the single size of nanoparticles and removal of exchange interaction between them. This feature leads to stability increase of particles.
The capacity increase is caused by nanometric size of particles. The problem associated with this situation is the subjection of material to ultra paramagnetic phase in which instable nanoparticles magnetic orientation are formed after field is cut off. To overcome this limitation we need a strong magnetic anisotropy.
"Production of magnetic nanoparticles through chemical synthesis and increasing their magnetic hardness by thermal treatment may bring about large coercivity in FePt nanoparticles after thermal treatment and create strong magnetocrystalline anisotropy,” Majid Farahmandjou, one of the researchers told the news service of the Iran Nano Technology Initiative Council (INIC).
As the first step, he dissolved FeCl2.4H2O, Pt (ac AC2, and hexadecanediol reductant in phenyl ether solvent at nitrogenic atmosphere. Then, he added oleic acid and oleylamine to the solution and heated it up to 200oC. At this temperature, a strong reductant called super hydride was added to the solution which resulted in fast release of metal atoms. After that, sample was purified in four steps. Finally, sample was left in a furnace containing Ar and H2 together with NaCl salt at 600 degrees C for a definite time. The result was a crystalline phase transition and magnetic coercivity enlargement.
The results of the present study show that stable FePt nanoparticles form after being heated at 700 degrees C in salt separation medium through ultrasonic process.
Details of the present study are found in the CHINESE JOURNAL OF PHYSICS, volume 47, pages 540 the 546, 2009.