Combined reactions associated with L10 ordering

Klemmer, T. J.; Liu, C.; Shukla, Nisha; Wu, Xiaowei; Weller, D.; Tanase, M.; Laughlin, David E.; Soffa, W.A.

doi:10.1016/s0304-8853(03)00458-x

Cited by 73 publications

(51 citation statements)

References 16 publications

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“…Nitric acid (Reachim, p.p.a. grade) and metal salts, Pt(AcAc) 2 (97 %, Aldrich) and Fe(AcAc) 3 (Reachim, p.p.a. grade), were used as received.…”

Section: Methodsmentioning

confidence: 99%

“…Due to the high magnetocrystalline anisotropy (K ∼ 6 × 10 7 erg cc -1 , 1 erg cc -1 = 10 -1 J m 3 ) of their chemically ordered face-centered tetragonal (fct) L1 0 phase, equiatomic FePt alloys have been recognized as one of the most promising candidates for future high-density recording media, which require thermally stable nanostructures with reduced dimensions.…”

mentioning

confidence: 99%

“…Similar to chemically synthesized FePt nanoparticles, those fabricated by gas condensation, vapor deposition, or sputtering processes also adopt the chemically disordered fcc structure if the particles do not reach sufficiently high temperature during growth. [3] Hence, high-temperature post-annealing is typically required to transform FePt particles into the L1 0 ordered phase. Several routes have been explored to prevent sintering or to produce fct nanoparticles in the as-fabricated state.…”

mentioning

confidence: 99%

“…However, this usually comes at the expense of grain growth. [3] Other approaches, such as rapid annealing, [7] which has shown moderate success, or non-traditional methods for annealing based on light absorption [8] or pulsed laser heating [9] have been explored recently. Post-deposition organic coating and self-assembly of gas-phase synthesized nanoparticles, [10] as well as pre-annealing at moderate temperatures, [11] aimed at decomposing the surfactant without sintering particles, have also been suggested.…”

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confidence: 99%

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

et al. 2006

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“…Nitric acid (Reachim, p.p.a. grade) and metal salts, Pt(AcAc) 2 (97 %, Aldrich) and Fe(AcAc) 3 (Reachim, p.p.a. grade), were used as received.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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

et al. 2006

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“…FePt nanoparticles are more difficult to transform because they do not have conventional grain boundaries and do not have many defects either. [9] Accordingly, any post-annealing approach usually results in particle agglomeration and twin formation, which will limit their applications. An alternative, and also optimal, way to prepare nanoparticles with the desired crystal structure is to control the thermal environment for their nucleation and growth, which is the main focus of this work.…”

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confidence: 99%

Tuning the Crystal Structure and Magnetic Properties of FePt Nanomagnets

Qiu

Wang

2007

Advanced Materials

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Ferromagnetic nanoparticles are important materials for nanotechnology both in practical applications and in fundamental research. The different purposes for which they are used have posed significant challenges in their preparation. For example, the development of highly sensitive magnetoresistive (MR) sensors makes it possible to detect the binding interactions between DNA or protein molecules, which are attached by magnetic beads.[1] To achieve high selectivity and sufficient signal-to-noise ratio, oxidation-resistive ferromagnetic nanomagnets are more favorable than the superparamagnetic microbeads usually used. Nanocomposite exchangespring magnets were expected to have unusually high energy products (BH) max (magnetic flux density times magnetic field strength), which requires the fabrication of crystallographically coherent hard and soft magnetic phases with a proper exchange coupling. [2,3] This requires nanometer-scale structure and property control of both the hard and soft magnetic components. Future extremely high density magnetic storage media demand high anisotropic magnetic materials, such as L1 0 -phase FePt, to overcome the superparamagnetic limit.[4]Chemical ordering and orientation control are essential prerequisites for the popular wet-chemical approach, [5] and these are difficult to achieve by post-deposition annealing. [6] We have recently reported a vacuum technique based on the gasphase condensation principle to prepare directly ordered FePt nanoparticles. [7] Here we present a general methodology of tuning the crystal structure and magnetic properties of FePt binary alloy nanomagnets.The final crystal structure of nanoparticles is a result of their thermal history, which involves both thermodynamic and kinetic factors. The binary phase diagram of equiatomic FePt alloy shows that it has two solid-state phases: fcc disordered (face-centered cubic or A1 phase) and fct ordered (face-centered tetragonal or L1 0 phase), with fcc as the high-temperature stable phase.[8] Many of the preparation techniques are kinetically controlled, so the fcc disordered phase dominates their final products. To get the fct ordered phase post-deposition annealing is generally used. This annealing process is a first-order phase transformation process, which requires nucleation sites for the ordering to originate. In FePt thin films, grain boundaries and crystal defects can supply such starting points for phase transformation. FePt nanoparticles are more difficult to transform because they do not have conventional grain boundaries and do not have many defects either.[9] Accordingly, any post-annealing approach usually results in particle agglomeration and twin formation, which will limit their applications. An alternative, and also optimal, way to prepare nanoparticles with the desired crystal structure is to control the thermal environment for their nucleation and growth, which is the main focus of this work. There are several different ways to control the thermal environment for particle nucleation and growth by ...

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L 1 ₀ Fept for Magnetic Recording Media Application

Piramanayagam

Chong

2011

Developments in Data Storage

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Combined reactions associated with L10 ordering

Cited by 73 publications

References 16 publications

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

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

Tuning the Crystal Structure and Magnetic Properties of FePt Nanomagnets

L 1 ₀ Fept for Magnetic Recording Media Application

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Combined reactions associated with L10 ordering

Cited by 73 publications

References 16 publications

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

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

Tuning the Crystal Structure and Magnetic Properties of FePt Nanomagnets

L 1 0 Fept for Magnetic Recording Media Application

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

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

L 1 ₀ Fept for Magnetic Recording Media Application