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M s and H c as functions of the annealing temperature for Fe 50 Pt 50 films with the annealing time of 30 min. The film thickness is 200 nm.
Source publication
Fe <sub>100-x</sub> Pt <sub>x</sub> alloy thin films with x=25–67 at. % were prepared by dc magnetron sputtering on naturally oxidized Si substrates. Effects of film composition, annealing temperature (300–650 °C), annealing time (5–120 min), and cooling rate (furnace cooling or ice water quench cooling) on the magnetic properties were investigat...
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Citations
... Although the remanence is slightly smaller than 0.9 T 20 and 0.8 T, 21 the obtained highest (BH)max value (100 kJ/m 3 ) was comparable to the values for the sputtered and arc-melted Fe-Pt thick-films. 22,23 Moreover, the annealing period of 7 sec to obtain high coercivity is much shorter than those of the previous reports (10 sec 24 and 300 sec 25 ). We confirmed the flash annealing method enables us to prepare Fe-Pt films with high hard-magnetic properties. ...
We prepared L10 ordered Fe50Pt50 thick-films on Cu substrates using the electroplating method and evaluated their high-temperature properties in the temperature range of 25-200°C. The Hc and the (BH)max at 150°C for the Fe50Pt50 films annealed by ordinary annealing method (700°C, 60 min) were 500 kA/m and 50 kJ/m³, respectively, and the thermal coefficient of Hc was -0.3%/°C. To improve the high-temperature properties, we employed a flash annealing method using an infrared furnace (8 kW). The flash annealing method improved the high-temperature properties (Hc = 700 kA/m, (BH)max = 70 kJ/m³ at 150°C) and the thermal coefficient (-0.21%/°C). The thermal stability of the films is comparable to those for Sm-Co-system magnets and better than for Nd-Fe-B-system ones. We, therefore, found the L10 ordered Fe50Pt50 films prepared by the electroplating and the flash annealing are one of the hopeful small magnets in the wide temperature range.
... The samples have been annealed at 500 C in air. The annealing temperature, T ann , has been selected considering possible chemical interaction with Si observed at T ann > 500 C [29]. The chemical composition of the metallic nucleus has been checked using the energy-dispersive X-ray (EDX) spectroscopy method as described elsewhere [32]. ...
We have prepared Fe-Pt and Fe-Pt- M (M = B, Si) microwires using Taylor-Ulitovsky technique and studied their magnetic properties. Magnetic properties considerably depend on the metallic core composition and annealing conditions. As-prepared microwires present either amorphous or mixture of amorphous and nanocrystalline phases with a presence of BCC FePt, FCC PtFe and small amount of tetragonal FePt phase. After annealing at 500 °C Fe50Pt40Si10 microwires we observed a remarkable magnetic hardening (coercivity increasing from 5 Oe up to 500 Oe) related to crystallization of as-prepared amorphous Fe50Pt40Si10 microwires. Annealed Fe50Pt50 sample present coercivity up to 800 Oe at 5K, but the magnetization of Fe50Pt50 sample is low and rapidly decreases with temperature. We discussed peculiarity of Fe50Pt50 microwires considering the influence of internal stresses on magnetic ordering of Fe-atoms.
... However, simply utilizing the TiN buffer layer is not sufficient to prohibit grain growth during the annealing process, while fine grain structure is very important for improving the recording precision and storage capacity [9]. In order to promote the formation of L1 0 -FePt phase by deposition at elevated temperature or by annealing, a rapid-quenching method can be applied, which is beneficial to control the grain size [10]. So far, major hurdles for the continuous FePt thin film are that the grains are not well separated and the strong exchange coupled effects will reduce the coercivity. ...
FePt thin films have been deposited on Si substrate with a TiN buffer layer. The effects of deposition temperature and the quenching rate on the magnetic properties and microstructure of the FePt/TiN films have been investigated. Out-of-plane anisotropy can be achieved for the film deposited at room temperature followed by annealing at 600 °C and quenching in air. It is observed that a small fraction of L10-FePt in the room temperature deposited film is well-aligned in the perpendicular direction which is due to the large surface energy of the TiN buffer layer, which contracts the lattice of L10-FePt during the ordering process. However, by increasing the deposition temperature from room temperature to 450 °C, both the L10-ordering parameter and the in-plane anisotropy can be enhanced. The microstructure and phase structural results indicate that a high quenching rate is beneficial to refine the FePt grains despite the high deposition temperature. The highest in-plane coercivity (915.6 kA/m) is obtained by depositing at 300 °C and quenching in air. However, when the film is deposited at 300 °C followed by quenching in ice water, the average FePt grain size dramatically decreases to 22 nm and the in-plane coercivity still maintains at about 875.8 kA/m. The results indicate that the high rate quenching can effectively separate the grains and result in the high coercivity due to the reduced exchange coupling effect.
... The formation of the ordered fct L1 0 FePt hard magnetic phase requires preheating the substrate or postannealing the as-deposited film at a high temperature of above 500°C. 6 However, this high temperature process results in grain growth, poor surface roughness, and interdiffusion between layers which decrease the recording density of the films and raise production costs. Therefore, a key challenge is to determine how to efficiently prevent the diffusion in a magnetic multilayer. ...
The thermal stability, interlayer diffusion, and magnetic properties of FePt(100 nm) single-layer and multilayer [Os(5 nm)/FePt(25 nm)]4 films on a Si(100) substrate with/without a 10-nm-thick Os underlayer have been studied as functions of the annealing temperatures between 400 and 800 °C. The insertion of a thin Os layer into the FePt and Si(100) interface results in better thermal stability. No diffusion evidence was found in samples with an Os underlayer for annealing temperatures up to 700 °C, as seen from x-ray, transmission electron microscopy, and magnetic studies. We have experimentally demonstrated that the Os underlayer can effectively prevent the diffusion of the intermixing between the FePt layer and the Si(100) substrate for temperatures up to 700 °C. As a result of this study, the Os has potential to be a better diffusion barrier to prevent the diffusion of the FePt film on a Si(100) substrate from forming an ordered face centered tetragonal (fct) L10 hard magnetic phase.
... Similar situation seems to occur also in real experimental conditions. 20,21) To generate the complete ordered phase structure, it is necessary to anneal the system gradually. We confirmed that the ordered phase structure is Order of FePt Alloy Clusters 2427 kept stably at even low temperatures once the ordered structure is formed around 1970 K and then slowly cooled down. ...
A realistic lattice gas model with a tetrahedral 4-body interaction is derived for a system composed of Fe, Pt atoms and vacancies on the basis of first-principles calculations. Using this model, we carry Out lattice Monte Carlo simulations of order-disorder phase transition in a bulk FePt alloy. aggregation into FePt clusters in vapor, and L1(0) ordering in FePt clusters. The order-disorder phase transition temperature of a bulk FePt is estimated to be 1970 K, which is slightly higher than the experimental value of 1572 K because of the ignorance of the off-lattice effects. The present model shows inherent atomic cohesion that leads to aggregation into clusters in a Simulation starting from a random configuration in vapor. Finally for FePt alloy clusters, we find that the L I a ordered structure is maintained only for those clusters with a size (diameter) greater than 2.5 nm, in accordance with the recent experimental evidence reported by Miyazaki et al. [doi: 10.2320/matertrans.MB2008261
... In addition, the SmCo 5 alloy has the advantage of low crystallization temperature. In the case of thin films, the temperature was reported to be 200 to 400 o C (7)(8)(9)(10)(11)(12), which is lower than the ordinary ordering temperature of L1 0 Fe-Pt alloy (13,14). Indeed, some researchers applied a Sm-Co alloy thin film to longitudinal magnetic recording media from as early as 1980's (8,(15)(16)(17). ...
Sputter-deposited SmCo5 thin films exhibiting high perpendicular magnetic anisotropy were studied for materializing ultra high density magnetic recording. This study put emphasis on the fabrication of SmCo5 double-layered perpendicular magnetic recording media. A double-layered medium with a Ru buffer layer introduced between a Cu/Ti intermediate layer and a Co-Zr-Nb soft magnetic underlayer exhibited high perpendicular magnetic anisotropy, whereas that without the Ru buffer layer did not. Auger electron spectroscopy revealed that the Ru buffer layer inhibited unfavorable interdiffusion between the Cu/Ti intermediate layer and the Co-Zr-Nb soft magnetic underlayer. In addition, the read-write characteristics of the SmCo5 double-layered perpendicular magnetic recording media were evaluated for the first time.
... The ordered face-centered-tetragonal (fct) FePt thin films have attracted much attention due to their potential applications in high-density recording media and the magnetic component of the micro-electromechanical systems [1,2]. Generally, FePt films are prepared by using sputtering [3,4], molecular beam epitaxy [5,6], electrodeposition [7,8], and solution phase chemical synthesis [9,10]. Compared with these preparation techniques, sol-gel method possesses distinctive advantages, such as inexpensive apparatus, facile operation, narrow particle size distribution, excellent chemical homogeneity, and low processing temperature [11,12]. ...
A simple sol-gel spin coating technique was used to fabricate FePt films. The effects of heating temperature on the film's crystalline structure, morphology and magnetic properties were investigated. In this paper, pure face-centered-tetragonal FePt films were obtained through calcining at 370 degrees C and subsequently reducing above 470 degrees C. Magnetic measurements indicated that the coercivity of up to 1.45 T and the squareness of up to 0.72 can be achieved in these films. (c) 2007 Elsevier B.V. All rights reserved.
... This hard magnetic performance is fairly good compared to those of some films annealed at about 500 °C. 3,4,6 But H c is not as high as those of films annealed at higher temperatures, 5-7 indicating a moderate ordering degree for the fct-FePt film prepared by our method. ...
A simple sol-gel spin-coating technique was developed to prepare FePt films. The calcining temperature was found to have great influences on the film's crystalline structure and magnetic properties. For this method, pure face-centered-tetragonal FePt film was finally obtained by calcining at 370 degrees C and subsequently reducing at 470 degrees C.
... Micromagnetism calculation showed that FePt/Fe 3 Pt exchange spring permanent magnet has an energy product of 34.5 MGOe [20]. However, its magnetic properties strongly depend on the composition and microstructure [21], so that structural modification is very important for this kind of materials. An energy product as high as 50 MGOe has been obtained in rapidly annealed nanoscale Fe/Pt multilayers [22]. ...
Series of [FePt(4min)/Fe(tFe)]10 multilayers have been prepared by RF magnetron sputtering and post-annealing in order to optimize their magnetic properties by structural designs. The structure, surface morphology, composition and magnetic properties of the deposited films have been characterized by X-ray diffractometer (XRD), Rutherford backscattering (RBS), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX) and vibrating sample magnetometer (VSM). It is found that after annealing at temperatures above 500 °C, FePt phase undergoes a phase transition from disordered FCC to ordered FCT structure, and becomes a hard magnetic phase. X-ray diffraction studies on the series of [FePt/Fe]n multilayer with varying Fe layer thickness annealed at 500 and 600 °C show that lattice constants change with Fe layer thickness and annealing temperature. Both lattice constants a and c are smaller than those of standard ones, and lattice constant a decreases as Fe layer deposition time increases. Only a slight increase in grain size was observed as Fe layer decreased in samples annealed at 500 °C. However, the increase in grain size is large in samples annealed at 600 °C. The coercivities of [FePt/Fe]n multilayers decrease with Fe layer deposition time, and the energy product (BH)max reaches a maximum in the samples with Fe layer deposition time of 3 min. Comparison of magnetic properties with structure showed an almost linear relationship between the lattice constant a and the coercivities of the FePt phase.
... It is also a good candidate of permanent magnets, and the theoretically predicted energy product is 90MGOe in exchange spring type FePt/Fe structures [5]. However, its magnetic properties strongly depend on its composition and structure [6]. By self-assembly of nano particles and subsequent annealing, exchange coupled FePt/Fe 3 Pt nanoparticles showed a high energy product of 20.1MGOe. ...
A series of [FePt(4min)/Fe(tFe)]10 multilayers were prepared by RF magnetron sputtering and post annealing. The structures, morphology, composition, and magnetic properties were measured by XRD, SEM, EDX and VSM. X-ray diffraction showed that lattice constants of FePt phase changed with Fe layer thickness and annealing temperature. Both a and c are smaller than the standard values and a decreases as the deposition time of Fe layer increases. The grain sizes of samples annealed at 500°C increase slightly, while those at 600°C increase sharply as Fe layer decreases. The coercivities decrease with the deposition time of Fe layer, and the energy product (BH)max reaches a maximum at Fe layer deposition time of 3 minutes.
