Abstract
This study investigated the ultrathin Cu(002) capping nano-island effects on the magnetic characterizations and microstructure of epitaxial FePt(001) films directly fabricated on MgO(001) substrates at the relatively low temperature of 300 °C via electron-beam deposition. The enhancement of the coercivity is attributed to the lowered exchange coupling of FePt magnetic grains that begun from Cu atom behavior of spreading in many directions mainly along grain boundaries due to its lower surface energy than that of pure Fe or Pt. The measurement of angular-dependent coercivity shows a tendency of a domain-wall motion shift toward the rotation of the reverse-domain type upon the thickness of the Cu capping nano-island layer atop the FePt films. The intergranular interaction was clarified by the Kelly–Henkel plot, which indicated that there was strong exchange coupling (positive δM) between neighboring grains in the FePt continuous films without Cu capping nano-islands. On the other hand, a negative δM value was gained when the FePt films were capped with a Cu(002) single layer, indicating that the Cu capping layer can be used to control the strength of intergrain exchange coupling between the adjacent FePt grains and thicker Cu(002) capping nano-islands toward magnetic isolation; thus, there was an existence of dipole interaction in our designed Cu/FePt composite structure of stacked films.
Highlights
Introduction published maps and institutional affilFePt L10 ordered (CuAu (I)-type) phase has undergone a fast and uninterrupted growth in recent years due to its excellent material properties containing mainly of high magnetocrystalline anisotropy constant (Ku ~108 erg/cm3 ), high saturation magnetization (Ms ~1100 emu/cc), high-anisotropy field (Ha ~120 kOe), high-energy products (BH)max, high Curie temperature (Tc ~480 ◦ C), and high environmental stability [1–8]
2-nm and (c) a 4-nm Cu capping nano-island layer taken by secondary electron image (SEI) mode, 2-nm and (c) aThe
Our work presents the way that a Cu capping nano-island layer atop the FePt films is different from the method of cosputtering or the co-evaporation technique, and better to keep the c-axis highly oriented and perpendicular to the film plane at the reduced temperature of 300 ◦ C, which is suitable
Summary
Introduction published maps and institutional affilFePt L10 ordered (CuAu (I)-type) phase has undergone a fast and uninterrupted growth in recent years due to its excellent material properties containing mainly of high magnetocrystalline anisotropy constant (Ku ~108 erg/cm3 ), high saturation magnetization (Ms ~1100 emu/cc), high-anisotropy field (Ha ~120 kOe), high-energy products (BH)max , high Curie temperature (Tc ~480 ◦ C), and high environmental stability [1–8]. The properties of high Ku Fe-based alloys could delay the problem of superparamagnetic effect and maintain enough thermal stability to overcome thermal fluctuation, even with a stable particle size down to the nanometer scale, which means these alloys have future potential applications, such as in excited spin ensemble of high-density electronic devices and magnetic recording media with storage densities surpassing 10 Tbits/in2 [9–12]. The nanocomposite and nanogranular ferromagnetic film structures fabricated at low-temperature conditions have attracted significant attention because of the decoupling of the intergranular interaction that could enhance the signal-to-noise ratio; they are considered more favorable for the generation magnetic storage media [13–23]. The spin Hall effect (SHE)-induced perpendicular magnetization reversal behavior is with pay significant attention due to its potential for future low-power memory and logic devices.
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