Origin of enhanced anisotropy in FePt-C granular films revealed by XMCD

Streubel, Robert; N’Diaye, Alpha T.; Srinivasan, Kumar; Ajan, Antony; Fischer, Peter

doi:10.1063/1.5092719

Cited by 3 publications

(5 citation statements)

References 14 publications

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“…The Fe spin [m s = (2.2±0.2) µ B ] and orbital [m o = (0.24±0.03) µ B ] moments per Fe atom are within experimental uncertainty unaffected by the copper concentration [Fig. 3(b)] and agree well with literature values [7,[21][22][23][24]. In other words, modifications to magnetic properties, i.e., magneto-crystalline anisotropy, coercive and saturation field, are either not related to the normal Fe magnetic moment and local atomic environment in normal direction, or too small to emerge from the background contributions.…”

Section: X-ray Absorption Spectroscopysupporting

confidence: 87%

“…The experimental uncertainty is given by the standard deviation of the corresponding inhomogeneous distributions. These variations are negligible compared with L1 0 FePt-C that show a significant decrease in grain size from (200±160) nm 2 down to (50±20) nm 2 for 40 mol.%C concentrations [7]. These observations corroborate that the formation of nanogranular media is driven by the BN and SiO 2 segregant independent of the Cu concentration.…”

Section: Structural Properties and Magnetic Hysteresis Loopssupporting

confidence: 61%

“…Please refer to References [2,3] for a detailed discussion on the terminology of constituents, segregants, and dopants. In a previous work on the spectroscopic study of FePt-C granular films [7], we identified the reduced demagnetization field (grain size) mediated by carbon as the primary cause for the improved magnetic properties with respect to HAMR applications.…”

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confidence: 99%

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The effect of Cu additions in FePt–BN–SiO₂ heat-assisted magnetic recording media

Streubel

N’Diaye

Srinivasan

et al. 2020

J. Phys.: Condens. Matter

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Structural and chemical order impact magnetic properties of solids, which are governed by spin–orbit coupling and exchange interaction. The ordered L10 phase of FePt is a key material to heat-assisted magnetic recording; to enable high storage density, a solid understanding is needed of structural and chemical disorder at small length scales, as well as associated modifications of the electronic band structure. Here, we investigate the effect of boron and copper additions (≲6 mol% Cu) on structural and magnetic properties of L10 FePt granular media. Two copper-driven mechanisms, although competing, can lead to improvements in both structural and magnetic properties. In particular, the Cu substitution on the Fe-site leads to a degradation of magnetic properties due to the delocalized electron orbitals originating from a larger Cu d-orbital occupancy. At the same time, Cu substitution leads to an enhanced crystallographic order and consequently magneto-crystalline anisotropy, which offsets the former effect to a large extent. Our study is based on magnetometry, x-ray absorption spectroscopy, ab-initio calculations and a phenomenological theory of disordered FePt granular media. We do not observe a sizable modification to Fe moments and electronic configuration; Cu reveals two different resonances associated with the presence and absence of Cu–B bonds that vary with total Cu concentration.

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Section: X-ray Absorption Spectroscopysupporting

confidence: 87%

Section: Structural Properties and Magnetic Hysteresis Loopssupporting

confidence: 61%

mentioning

confidence: 99%

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The effect of Cu additions in FePt–BN–SiO₂ heat-assisted magnetic recording media

Streubel

N’Diaye

Srinivasan

et al. 2020

J. Phys.: Condens. Matter

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“…A typical reduction of the exchange interaction with increasing temperature or decreasing concentration of magnetic elements decreases both spin and orbital moment, and preserves their ratio. A high degree of orbital alignment manifests a large orbital moment as reported in L1 0 FePt [53]. We observe a significant drop of the orbital-to-spin-moment ratio both as a function of Fe concentration (x 0.61) and temperature, e.g., near 140 K for x = 0.52 [Figure 1(d)].…”

supporting

confidence: 74%

Chiral spin textures in amorphous iron germanium thick films

Streubel

2021

Spintronics XIV

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Topological solitary fields, such as magnetic and polar skyrmions, are envisioned to revolutionize microelectronics. These configurations have been stabilized in solid-state materials with a global inversion symmetry breaking, which translates in magnetic materials into a vector spin exchange known as the Dzyaloshinskii-Moriya interaction (DMI), as well as spin chirality selection and isotropic solitons. This work reports experimental evidence of threedimensional chiral spin textures, i.e., helical spins and skyrmions with different chirality and topological charge, stabilized in amorphous Fe-Ge thick films. These results demonstrate that structurally and chemically disordered materials with a random DMI, can resemble inversion symmetry broken systems with similar magnetic properties, 1 moments, and states. Disordered systems are distinguished from systems with global inversion symmetry breaking by their degenerate spin chirality that allows for forming isotropic and anisotropic topological spin textures at remanence while offering greater flexibility in materials synthesis, voltage and strain manipulation.The discovery of unprecedented physical properties and application potential of topologically protected non-collinear states in condensed matter has greatly influenced the direction of basic sciences of magnetic and ferroelectric materials. Magnetic [

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“…A high degree of orbital alignment manifests a large orbital moment as reported in L 1 0 FePt. [ 53,54 ] We observe a significant drop of the orbital‐to‐spin‐moment ratio both as a function of Fe concentration ( x ≲ 0.61) and temperature, for example, near 140 K for x = 0.52 (Figure 1d). As shown below, the suppression of the orbital moment coincides with the emergence of non‐collinear helical spin textures.…”

Section: Figurementioning

confidence: 96%

Chiral Spin Textures in Amorphous Iron–Germanium Thick Films

et al. 2021

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Topological solitary fields, such as magnetic and polar skyrmions, are envisioned to revolutionize microelectronics. These configurations have been stabilized in solid-state materials with a global inversion symmetry breaking, which translates in magnetic materials into a vector spin exchange known as the Dzyaloshinskii-Moriya interaction (DMI), as well as spin chirality selection and isotropic solitons. This work reports experimental evidence of 3D chiral spin textures, such as helical spins and skyrmions with different chirality and topological charge, stabilized in amorphous Fe-Ge thick films. These results demonstrate that structurally and chemically disordered materials with a random DMI can resemble inversion symmetry broken systems with similar magnetic properties, moments, and states. Disordered systems are distinguished from systems with global inversion symmetry breaking by their degenerate spin chirality that allows for forming isotropic and anisotropic topological spin textures at remanence, while offering greater flexibility in materials synthesis, voltage, and strain manipulation. The discovery of unprecedented physical properties and application potential of topologically protected non-collinear states in condensed matter has greatly influenced the direction of

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Origin of enhanced anisotropy in FePt-C granular films revealed by XMCD

Cited by 3 publications

References 14 publications

The effect of Cu additions in FePt–BN–SiO₂ heat-assisted magnetic recording media

The effect of Cu additions in FePt–BN–SiO₂ heat-assisted magnetic recording media

Chiral spin textures in amorphous iron germanium thick films

Chiral Spin Textures in Amorphous Iron–Germanium Thick Films

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Origin of enhanced anisotropy in FePt-C granular films revealed by XMCD

Cited by 3 publications

References 14 publications

The effect of Cu additions in FePt–BN–SiO2 heat-assisted magnetic recording media

The effect of Cu additions in FePt–BN–SiO2 heat-assisted magnetic recording media

Chiral spin textures in amorphous iron germanium thick films

Chiral Spin Textures in Amorphous Iron–Germanium Thick Films

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The effect of Cu additions in FePt–BN–SiO₂ heat-assisted magnetic recording media

The effect of Cu additions in FePt–BN–SiO₂ heat-assisted magnetic recording media