Structural studies of L10 FePt nanoparticles

Klemmer, T. J.; Shukla, Nisha; Liu, C.; Wu, Xiaowei; Svedberg, Erik B.; Mryasov, O. N.; Chantrell, R.W.; Weller, D.; Tanase, M.; Laughlin, David E.

doi:10.1063/1.1507837

Cited by 157 publications

(104 citation statements)

References 3 publications

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“…1, 3 Recently, there has been much attention placed on the chemical synthesis of self-assembled, monodispersed, and chemically ordered L1 0 ͑tetragonal phase͒ FePt nanoparticles for future ultrahigh-density magnetic storage. [4][5][6][7][8] In fact, recent advances in magnetic recording technology have indicated that, if self-assembled in a tightly packed, exchangedecoupled array with controlled magnetic easy axis direction, these FePt nanoparticles could support high-density magnetization reversal transitions and would be a candidate for future ultrahigh-density data storage media [8][9][10] with potentially one bit per particle corresponding to storage densities of 20 Tbit/ in. 2 The tetragonal phase of an FePt system is of particular interest because of the high magnetocrystalline anisotropy ͓K U ϳ͑6.6− 10͒ ϫ 10 7 erg/ cm 3 ͔ that should allow the use of smaller particles, but yet avoid thermal instabilities that give rise to superparamagnetic ͑SPM͒ behavior.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence and magnetocrystalline anisotropy studies of self-assembled L10-Fe55Pt45 ferromagnetic nanocrystals

Varanda

Jafelicci

Imaizumi

2007

Journal of Applied Physics

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Temperature dependence and uniaxial magnetocrystalline anisotropy properties of the chemically synthesized 4 nm L1 0 -Fe 55 Pt 45 nanoparticle assembly by a modified polyol route are reported. As-prepared nanoparticles are superparamagnetic presenting fcc structure, and annealing at 550°C converts the assembly into ferromagnetic nanocrystals with large coercivity ͑H C Ͼ 1 T͒ in an L1 0 phase. Magnetic measurements showed an increasing in the ferromagnetically ordered fraction of the nanoparticles with the annealing temperature increases, and the remanence ratio, S = M R / M S Х 0.76, suggests an ͑111͒ textured film. A monotonic increase of the blocking temperature T B , the uniaxial magnetocrystalline anisotropy constant K U , and the coercivity H C with increasing annealing temperature was observed. Magnetic parameters indicate an enhancement in the magnetic properties due to the improved Fe 55 Pt 45 phase stabilizing, and the room-temperature stability parameter of 67, which indicates that the magnetization should be stable for more than ten years, makes this material suitable for ultrahigh-density magnetic recording application.

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Section: Introductionmentioning

confidence: 99%

Temperature dependence and magnetocrystalline anisotropy studies of self-assembled L10-Fe55Pt45 ferromagnetic nanocrystals

Varanda

Jafelicci

Imaizumi

2007

Journal of Applied Physics

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“…Besides, AF domains have highly minimized dipolar magnetic interaction between the neighboring bits, and could play a crucial role in reducing the density of the current magnetic storage device 49 . Additionally such AF multilayers can be an integral part of an exchange biased system and could have significant impact in the quest of ultra-fast magnetic switching 55,56 .…”

Section: Analysis and Discussion Of The Resultsmentioning

confidence: 99%

“…It is also worthwhile to investigate the impact of Na ions on the magnetic anisotropy energy (MAE) which determines the stability of magnetic systems. In this regard materials with FePt composition are known to have high MAE 14,47,48 and are used for the current high density recording media 49 . Here, we show that MAE of FePt multilayer can be further enhanced by adsorption of Na ions.…”

Section: Magnetic Hardening Of Fept Multilayers With Na Ionsmentioning

confidence: 99%

Direct surface charging and alkali-metal doping for tuning the interlayer magnetic order in planar nanostructures

Dasa

Stepanyuk

2015

Phys. Rev. B

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The continuous reduction of magnetic units to ultra small length scales inspires efforts to look for a suitable means of controlling magnetic states. In this study we show two surface charge alteration techniques for tuning the interlayer exchange coupling (IEC) of ferromagnetic layers separated by paramagnetic spacers. Our ab − initio study reveals that already a modest amount of extra charge can switch the mutual alignment of the magnetization from anti-ferromagnetic to ferromagnetic or vice verse. We also propose adsorption of alkali metals as an alternative way of varying the electronic and chemical properties of magnetic surfaces. Clear evidence is found that the interlayer magnetic order can be reversed by adsorbing alkali metals on the magnetic layer. Moreover, alkali metal overlayers strongly enhance the perpendicular magnetic anisotropy in FePt thin films. These findings combined with atomistic spin model calculations suggest that electronic or ionic way of surface charging can have a crucial role for magnetic hardening and spin state control.

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“…Since the atomic ordering was promoted with the increase of substrate temperature, the degree of atomic order was considered to be very low in the case of specimens deposited at the substrate temperatures of 563 and 583 K. By contrast, the atomic ordering for the specimen deposited at 613 K was much promoted and, simultaneously, the coercivity was also increased with the decrease of axial ratio c=a as shown in the later section 3. ) or FePt nanoparticles (c=a ¼ 0:961, 19) c=a ¼ 0:966 26) ). Here S denotes the LRO parameter.…”

Section: à2mentioning

confidence: 99%

Low-Temperature Atomic Ordering of Oriented L1<SUB>0</SUB>-FePtCu Nanoparticles with High Areal-Density Characterized by Transmission Electron Microscopy and Electron Diffraction

2007

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Oriented and densely dispersed L1 0 -FePtCu nanoparticles have been directly synthesized by co-evaporation of Fe, Pt and Cu using rfmagnetron sputtering onto NaCl substrate kept at 563-613 K without any post-deposition annealing. Formation of the L1 0 -type structure in the specimens fabricated as low a substrate temperature as 563 K (Fe 40 Pt 50 Cu 10 ) was confirmed by electron microscopy and electron diffraction, while the coercivity measured at room temperature was very low and the intensity of the superlattice reflections was quite weak. The atomic ordering was promoted in the specimen fabricated at 613 K with a composition of Fe 37 Pt 52 Cu 11 , resulted in a higher coercivity exceeding 1 kOe at room temperature as well as appearance of clear superlattice reflections. In addition to the evolution of atomic ordering, h100i oriented growth was enhanced as the substrate temperature increased. Particle size dependence of long-range order (LRO) is considered to be responsible for the decrease of coercivity with particle size reduction as well as thermal fluctuation of magnetization. High coercivity was obtained for specimens with Cu concentration near 10 at% under the present sputtering condition. The LRO in the FePtCu ternary phase is considered to sensitively depend on the alloy concentration.

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Structural studies of L10 FePt nanoparticles

Cited by 157 publications

References 3 publications

Temperature dependence and magnetocrystalline anisotropy studies of self-assembled L10-Fe55Pt45 ferromagnetic nanocrystals

Temperature dependence and magnetocrystalline anisotropy studies of self-assembled L10-Fe55Pt45 ferromagnetic nanocrystals

Direct surface charging and alkali-metal doping for tuning the interlayer magnetic order in planar nanostructures

Low-Temperature Atomic Ordering of Oriented L1<SUB>0</SUB>-FePtCu Nanoparticles with High Areal-Density Characterized by Transmission Electron Microscopy and Electron Diffraction

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