Magnetic properties of FePt nanodots formed by a self-assembled nanodot deposition method

Abstract

Fe 50 Pt 50 nanodots dispersed in a SiO2 film (Fe50Pt50 nanodot film) were formed by a self-assembled nanodot deposition (SAND) method in which Fe50Pt50 and SiO2 are cosputtered in a high vacuum rf magnetron sputtering equipment. Fe50Pt50 pellets are laid on a SiO2 target in a sputtering chamber to form the Fe50Pt50 nanodot film in the SAND method. The size and density of Fe50Pt50 nanodot were controlled by changing the ratio of the total area of Fe50Pt50 pellets to that of SiO2 target. The Fe50Pt50 nanodot size decreases and its density increases when the ratio decreases. As-deposited Fe50Pt50 nanodots self-assembled to a face-centered-cubic phase of single-crystal structure. The Fe50Pt50 nanodot films were annealed to evaluate the nanodot size controllability, the magnetic anisotropy, and the thermal stability. Fully ordered L10 face-centered-tetragonal Fe50Pt50 nanodots with high magnetocrystalline anisotropy (Ku≅8.7×107ergs∕cm3) were obtained by in situ annealing at 600°C for 1h in a high vacuum ambience. Furthermore, the Fe50Pt50 nanodot film with a monolayer of Fe50Pt50 nanodots was formed by annealing at 800°C due to the agglomeration of Fe50Pt50 nanodots in the SiO2 film.

New Magnetic Nanodot Memory with FePt Nanodots

“…The FePt alloy with an L1 0 face-centered tetragonal (fct) structure has high magnetocrystalline anisotropy. [4][5][6][7][8][9] In this study, the FePt alloy was employed as a magnetic nanodot retention layer. Furthermore, self-assembled nanodot depositon (SAND) has been employed for the fabrication of the FePt MND films.…”

“…Furthermore, self-assembled nanodot depositon (SAND) has been employed for the fabrication of the FePt MND films. [1][2][3][4] Figure 2 schematically shows the SAND method, where FePt pellets lay on the SiO 2 target to cosputtered in the highvacuum rf magnetron sputtering equipment. The target ratio of FePt/SiO 2 was defined as a ratio of the area of FePt pellets to the surface area of a SiO 2 target where the FePt pellets are placed.…”

“…After annealing at 600 C for 1 h, all of the fct peaks appeared including the (002) peak, indicating that the FePt nanodots convert into an L1 0 fct phase. 4,5) Figure 6 shows the temperature dependence of coercivity (H c ) on the FePt-SiO 2 film after annealing at 600 C for 1 h measured using a superconducting quantum interference device (SQUID). The coercivities (H c ) of the FePt nanodots measured at 293, 100, and 10 K, were 11.5, 17.5, and 21.5 kOe, respectively.…”

Fabrication and magnetic properties of FePt/Ag multilayered nanowires

“…Recently with the upsurge of nano-technology, many kinds of ordering nano-structured materials such as quantum dots, nanotubes and nanowires are studied [1][2][3]. Nanopatterned magnetic recording media offer a number of advantages over conventional continuous magnetic recording media, including the ability to provide a much higher recording density [4][5][6].…”

Microstructure and magnetic properties of FePt-SiO2 granular films with Ag addition

“…Many investigations on the fabrication of the FePt granular films by the sputtering technique have been made. [22][23][24][25][26][27][28] However, controlling the particle size is difficult since most of the granular films are deposited at room temperature, and a postannealing becomes necessary for the L1 0 ordering. Okamoto et al fabricated FePt-AlN and FePt-MgO granular films on heated MgO substrates; 22 however, the average particle size was too large to be considered for the high-density recording media.…”