Castaldi L, Giannakopoulos K, Travlos A, Niarchos D, Boukari S, Beaurepaire E
IMS, NCSR 'Demokritos', Agìa Paraskevi Attiki, 153 10, Greece.
Nanotechnology. 2008 Feb 27;19(8):085701. doi: 10.1088/0957-4484/19/8/085701. Epub 2008 Feb 4.
We compare CoPt and FePt nanoparticles grown under identical conditions on oxidized Si substrates by electron beam co-evaporation. Growth was performed under high vacuum conditions at substrate temperatures of 1023 K and was immediately followed by an annealing step. This process forms CoPt and FePt nanoparticles with mean diameters between ∼17 and ∼22 nm. In particular, the annealing step results in grain size enlargement for all samples and in a progressive magnetic hardening of the nanoparticles which reach maximum perpendicular coercivities of ∼6.6 kOe (for the CoPt) and ∼10.2 kOe (for the FePt nanoparticles). We show that, during this annealing step, a progressive transition towards the hard magnetic L1(0) ordered phase takes place in both materials. In contrast to FePt, CoPt nanoparticles must be annealed in order to crystallize in this phase.
我们通过电子束共蒸发比较了在相同条件下生长在氧化硅衬底上的CoPt和FePt纳米颗粒。生长过程在高真空条件下于1023 K的衬底温度下进行，随后立即进行退火步骤。此过程形成平均直径在约17至约22 nm之间的CoPt和FePt纳米颗粒。特别地，退火步骤导致所有样品的晶粒尺寸增大，并且纳米颗粒逐渐磁硬化，达到约6.6 kOe（对于CoPt）和约10.2 kOe（对于FePt纳米颗粒）的最大垂直矫顽力。我们表明，在该退火步骤期间，两种材料都向硬磁L1(0)有序相发生逐渐转变。与FePt不同，CoPt纳米颗粒必须进行退火才能在该相中结晶。
