Formation of FePt–MgO Nanocomposite Films at Reduced Temperature

Abstract

The MgO nanolayer effect on the microstructure and magnetic characterizations added into Fe/Pt stacked films directly deposited onto MgO (001) single-crystal substrates at the reduced temperature of 380 °C using electron-beam technology was investigated in this present work. The nanograin isolation and exchange decoupling for the FePt–MgO system is attributed to the magnetic FePt isolated grains that originate from MgO atoms with a spreading behavior mostly along grain boundaries owing to its weaker surface energy than that of a single Fe or Pt element. The grain and domain size decreased when the MgO nanolayer was applied due to the interpenetration of MgO and created a strain-energy variation at the MgO/FePt interface. Measuring angular-dependent coercivity indicates a general trend of a domain-wall motion, and changes to the rotation of the reverse-domain model occurred as the MgO nanolayers were added into FePt films. The intergrain interaction is confirmed by the Kelly–Henkel plot, which shows that there is strong intergrain exchange coupling (positive δM type) between neighboring grains in the continuous Fe/Pt stacked films without MgO nanolayers. In addition, a negative δM type occurred when the Fe/Pt stacked films were added into MgO nanolayers, showing that the MgO nanolayer can be applied to adjust the force of intergrain exchange coupling between the adjacent FePt nanograins, and the addition of MgO nanolayers change into magnetic decoupling; thus, there was a formed dipole interaction in our claimed FePt–MgO composite structure of stacked ultrathin films at a reduced temperature of 380 °C.

Editorial for the Special Issue on Magnetic and Spin Devices, Volume II

“…Simulations with an Ising annealing system constructed using 64 such spins demonstrated factorization of n-bit integers up to 2 64 with a temporal complexity proportional to √ n. Heat-assisted magnetic recording (HAMR) technology is a promising alternative to replace the current perpendicular magnetic recording, further increasing the areal density of hard disk drives; however, unwanted noise may affect the read-back signal. The transition jitter noise at ultrahigh areal density in L1 0 -FePt-based [13] HAMR technology was explored by means of micromagnetic simulations in Contribution 5. The lowest transition jitter was obtained in an 8 nm track width at a 9 nm bit length, yielding a projected ultrahigh areal density of 8.9 Tb/in 2 for upcoming applications.…”