In this work, we prepared the nanocrystalline near-equiatomic FePt thin films by electrodeposition and explored the effects of annealing temperature and annealing time on morphology, structure, and magnetic properties of FePt film. The fcc-FePt phase starts to form when annealing at 400 °C under the 15% H₂ gas mixture. With increasing annealing temperature from 400 to 800 °C, the FePt film experiences a gradual phase transformation from the soft magnetic fcc phase to the permanent magnetic fct L1₀ phase. The transition degree of the L1₀ phase is achieved to be 0.94 and coercivity reaches a maximum of 1.5 T for the sample annealed at 800 °C for 4 h. A shoulder behavior in the M(H) curves is found in the electrodeposited FePt films. Through fitting the M(H) curves by the model based on the transition degree of the L1₀ FePt phase, the shoulder behavior is quantitatively confirmed to originate from the coexistence of the soft magnetic fcc phase and the permanent magnetic L1₀ phase. The magnetic exchange coupling between the soft magnetic and permanent magnetic nanocrystalline phases is negligible in the electrodeposited FePt films due to that the substrate Ag diffusion into the FePt film separates the FePt nanocrystalline phases.

在这项工作中，我们通过电沉积制备了纳米晶近等原子的FePt薄膜，并探索了退火温度和退火时间对FePt薄膜的形态，结构和磁性的影响。当在15％H ₂气体混合物中于400°C退火时，fcc-FePt相开始形成。随着退火温度从400°C升高到800°C，FePt膜经历了从软磁性fcc相到永久磁性fct L1 ₀相的逐渐相变。对于在800°C退火4 h的样品，L1 ₀相的转变度达到0.94，矫顽力达到1.5 T的最大值。在M（H）曲线在电沉积的FePt膜中发现。通过基于L1 ₀ FePt相的转变程度的模型拟合M（H）曲线，定量地确定了肩部行为是由于软磁fcc相和永磁L1 ₀相的共存引起的。在电沉积的FePt膜中，软磁性和永久磁性纳米晶相之间的磁交换耦合可忽略不计，因为衬底Ag扩散到FePt膜中使FePt纳米晶相分离。