Columnar Structure in FePt–C Granular Media for Heat-Assisted Magnetic Recording

Varaprasad, B. S. D. Ch. S.; Wang, Jian; Shiroyama, T.; Takahashi, Y. K.; Hono, K.

doi:10.1109/tmag.2015.2435027

Cited by 39 publications

(18 citation statements)

References 25 publications

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“…The single crystalline L1 0 FePt grains were grown epitaxially onto a single-crystal MgO(001) substrate by co-sputtering Fe, Pt and C. 28 Figure 1a shows that individual nanoparticles remained aligned during this process, as the particles were held in place by the carbon matrix. The nanoparticles were characterized using transmission electron microscopy (see Fig.…”

Section: Sample Preparation and Characterizationmentioning

confidence: 99%

Beyond a phenomenological description of magnetostriction

et al. 2018

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Magnetostriction, the strain induced by a change in magnetization, is a universal effect in magnetic materials. Owing to the difficulty in unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how the source of magnetostriction—the underlying magnetoelastic stress—can be separated in the time domain, opening the door for an atomistic understanding. X-ray and electron diffraction are used to separate the sub-picosecond spin and lattice responses of FePt nanoparticles. Following excitation with a 50-fs laser pulse, time-resolved X-ray diffraction demonstrates that magnetic order is lost within the nanoparticles with a time constant of 146 fs. Ultrafast electron diffraction reveals that this demagnetization is followed by an anisotropic, three-dimensional lattice motion. Analysis of the size, speed, and symmetry of the lattice motion, together with ab initio calculations accounting for the stresses due to electrons and phonons, allow us to reveal the magnetoelastic stress generated by demagnetization.

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Section: Sample Preparation and Characterizationmentioning

confidence: 99%

Beyond a phenomenological description of magnetostriction

et al. 2018

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“…This deposition method leads to formation of columnar FePt grains in the FePt-C film with a thickness larger than 6 nm. 22 The thicknesses of the films, the atomic ratio of Fe and Pt, and the volume fraction of carbon were estimated using the pre-calibrated sputtering rates for the above elements, and the average deposition rate was controlled to be 0.71 nm/min. The compositions of the FePt grains estimated by energy dispersive x-ray spectroscopy were about Fe 50 Pt 50 for all the films.…”

Section: Methodsmentioning

confidence: 99%

“…However, we should note that recent work on the structural optimization of the FePt-C system by using a compositionally graded sputtering process has shown that an excellent columnar structure with a fine grain size can be grown even on single-crystalline MgO(001) substrates. 22 Hence, better control of the carbon concentration during growth of the FePt-C layer may lead to formation of columnar grains regardless of the grain size of the MgO underlayer. The important insight obtained in this study is the critical importance of controlling the particle coalescence and subsequent grain coarsening for controlling the microstructure of the FePt-C layers.…”

Section: Role Of the Mgo Grain Boundarymentioning

confidence: 99%

“…The important insight obtained in this study is the critical importance of controlling the particle coalescence and subsequent grain coarsening for controlling the microstructure of the FePt-C layers. The density of nuclei is more than enough, so suppression of the coarsening of the FePt grains by, for example, increasing the carbon concentration in a later stage 22 or doping heavy elements that are insoluble with FePt may lead to columnar grain growth with a substantially smaller grain size.…”

Section: Role Of the Mgo Grain Boundarymentioning

confidence: 99%

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Influence of MgO underlayers on the structure and magnetic properties of FePt-C nanogranular films for heat-assisted magnetic recording media

et al. 2016

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In order to optimize the nanogranular structure of FePt-C for heat-assisted magnetic recording media, we investigated the influence of MgO underlayers on the growth of FePt grains in the FePt-C layer. The FePt-C layer was deposited by using the alternating sputtering method, by which FePt and FePt-C layers were alternately deposited. To understand the growth mechanism of the FePt-C layer on the MgO underlayers deposited under various conditions, detailed plan-view and cross sectional transmission electron microscopy observations were made for different film thicknesses. We found that columnar FePt grains grow only when the deposition conditions of the MgO underlayer are optimal. Direct TEM observation of the growth process of the FePt-C layer revealed that the number density of nuclei is sufficient in the initial stage of the film deposition; however, coarsening of the grains after grain impingement causes a substantial decrease in the number density of the FePt grains.

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“…The carbon segregant shows strong phase separation ability and can easily interrupt the FePt columnar grain growth laterally. The FePtC film shows a uniform in-plane granular grains structure but with the spherical grains and second nucleated FePt layer (t > 6 nm) in cross-sectional TEM images [6]. In addition to the C single segregant, the transition-metal oxide segregants were also required and have been extensively studied before now [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Magnetic Properties and Microstructure of FePt(BN, Ag, C) Films

Tsai

Chen

et al. 2018

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The microstructure and magnetic properties of FePt(BN, Ag, C) granular films grown on the MgTiON intermediate layer with and without the MoC inserting layer were studied. Without the MoC inserting layer, the 6 nm thick FePt film is continuous, which favors the domain wall motion magnetization reversal process and shows a lower out-of-plane coercivity (Hc) value of 6.7 kOe. The FePt(BN, Ag, C) granular film was grown in ball- and square-like grains with an almost vertical contact angle, and the out-of-plane coercivity (Hc) was increased to 15.5 kOe. When the MoC with a thickness of 3 nm was capped on the MgTiON intermediate layer, the FePt grains with and without (BN, Ag, C) segregants were both formed in large trapezoidal islands with a low contact angle morphology. The out-of-plane Hc value changed from 14.9 to 13.2 kOe and the reduced coercivity was due to larger grain sizes and a lower ordering degree of the FePt(BN, Ag, C) film.

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Columnar Structure in FePt–C Granular Media for Heat-Assisted Magnetic Recording

Cited by 39 publications

References 25 publications

Beyond a phenomenological description of magnetostriction

Beyond a phenomenological description of magnetostriction

Influence of MgO underlayers on the structure and magnetic properties of FePt-C nanogranular films for heat-assisted magnetic recording media

Magnetic Properties and Microstructure of FePt(BN, Ag, C) Films

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