Microstructural characterization of L1 FePt/MgO nanoparticles with perpendicular anisotropy

Abstract

L 1 0 FePt nanoparticles with perpendicular magnetic anisotropy were fabricated on a heated MgO substrate by using an atomic deposition technique. The microstructure of the FePt nanoparticles was studied by transmission electron microscopy and high resolution transmission electron microcopy. The as-made L10 FePt nanoparticles are isolated and have a faceted morphology with a bimodal distribution of particle size as small as 2.5 nm. A semicoherent atomic interface between the FePt nanoparticles and the MgO substrate is observed. The room temperature coercivity of these FePt nanoparticles was measured via both superconducting quantum interference device and magneto-optical Kerr effect techniques and found to be as high as 6.7 kOe.

Direct Synthesis of Isolated L10 FePt Nanoparticles in a Robust TiO2 Matrix via a Combined Sol–Gel/Pyrolysis Route

“…Particles with the same magnetocrystalline anisotropy but different sizes will have different thermal stabilities (due to the different anisotropy energy per particle, E = K V, where V is the nanoparticle volume) and hence different coercivities. It was shown in a recent study [18] that particles with sizes as small as 3 nm could still adopt the fct structure; however, enhanced surface effects are expected to progressively modify the spin configuration [25] and, consequently, the hysteresis loop shape. [26] On the other hand, the degree of structural order and hence the magnetocrystalline anisotropy is known to depend on the Fe/Pt ratio.…”

“…[15,16] Moreover, some progress towards the direct, one-step synthesis of tetragonal FePt particles (i.e., without first obtaining fcc nanoparticles) appears achievable via a recently reported polyol synthesis method [17] and by deposition on a substrate at elevated temperatures. [18] However, in spite of these significant efforts, preventing the undesired sintering during the fcc-fct phase transformation continues to be a significant challenge. The intermatrix synthesis is an alternative route to be explored for the one-step synthesis of tetragonal FePt particles.…”

Effects of non-magnetic phase and deposition temperature on magnetic properties of FePt–MgO granular thin films on single-crystal MgO substrate

“…It was reported that some researchers attempted to obtain the granular microstructure by using various non-magnetic materials [2][3][4] . MgO is chosen for its widely application in the tunnel junction devices and has a suitable lattice mismatch with FePt (4%) [5][6][7] .In general, FePt-MgO nano-granular film can be formed by either FePt/MgO multilayer deposition or co-sputtering of FePt and MgO after the annealing [8][9] . Nevertheless, excessive amount of MgO non-magnetic phase will degrade the transformation of L1 0 -FePt [10] .…”

Magnetic properties of <italic>L</italic>1<sub>0</sub>-FePt(001)/<italic>A</italic>1-FePt bilayer exchange springs

“…FePt 合 金 在 常 温 环 境 中 还 存 在 一 种 具 有 面 心 立 方 (face centered cubic, FCC)晶体结构的亚稳相(用A1表 示, 可以认为是高温相的过冷态), Fe和Pt原子随机出 现在格点位置, 不具备成分有序的特征. 在常温获得 的FePt薄膜通常都处于A1相, 需要经过适当的热处 理, 才能转变为更稳定的L1 0 相 [21,22] . A1-FePt也具有 铁 磁 性 , 但 立 方 磁 晶 各 向 异 性 能 很 低 .…”