Fast magnetization precession observed in L1-FePt epitaxial thin film

Mizukami, Shigemi; Iihama, Satoshi; Inami, Nobuhito; Hatori, Takashi; Kim, G.; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo

doi:10.1063/1.3549704

Cited by 109 publications

(105 citation statements)

References 22 publications

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“…5, corresponding to 0 ≤ S ≤ 0.985, are appreciably smaller than the measured one which amounts to α ≈ 0.06 reported for a thin L1 0 FePt epitaxial film. 54 The high measured value of α might be thus explained by the present calculations by assuming a very small concentration of antisites in the prepared films, which does not seem too realistic. Another potential source of the discrepancy lies in the thin-film geometry used in the experiment.…”

Section: Fept Alloys With a Partial Long-range Ordermentioning

confidence: 81%

Nonlocal torque operators inab initiotheory of the Gilbert damping in random ferromagnetic alloys

2015

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We present an ab initio theory of the Gilbert damping in substitutionally disordered ferromagnetic alloys. The theory rests on introduced nonlocal torques which replace traditional local torque operators in the well-known torque-correlation formula and which can be formulated within the atomic-sphere approximation. The formalism is sketched in a simple tight-binding model and worked out in detail in the relativistic tight-binding linear muffin-tin orbital (TB-LMTO) method and the coherent potential approximation (CPA). The resulting nonlocal torques are represented by nonrandom, non-site-diagonal and spin-independent matrices, which simplifies the configuration averaging. The CPA-vertex corrections play a crucial role for the internal consistency of the theory and for its exact equivalence to other first-principles approaches based on the random local torques. This equivalence is also illustrated by the calculated Gilbert damping parameters for binary NiFe and FeCo random alloys, for pure iron with a model atomic-level disorder, and for stoichiometric FePt alloys with a varying degree of L10 atomic long-range order.

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Section: Fept Alloys With a Partial Long-range Ordermentioning

confidence: 81%

Nonlocal torque operators inab initiotheory of the Gilbert damping in random ferromagnetic alloys

2015

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“…The question is still open whether the well developed theories can shed light on the damping behavior in such materials, and therefore motivates extensive research [31,[38][39][40][41][42][43]. For instance, S. Mizukami et al demonstrated a low value of α 0 with considerable K u in MnGa alloys, due to the low density of states at the Fermi level, D(E F ) [40].…”

Section: Introductionmentioning

confidence: 99%

Role of antisite disorder on intrinsic Gilbert damping inL10FePt films

et al. 2015

Phys. Rev. B

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The impact of anti-site disorder x on the intrinsic Gilbert damping α 0 in well-ordered 1 FePt films is investigated by time-resolved magneto-optical Kerr effect. The variation of x mainly affects the electron scattering rate 1/τ e , while other leading parameters remain unchanged. The experimentally observed linear dependence of α 0 on 1/τ e indicates that spin relaxation is through electron interband transitions, as predicted by spin-orbit coupling torque correlation model. Measurements at low temperature show that α 0 remains unchanged with temperature even for FePt with very high chemical order, indicating that electron-phonon scattering is negligible. Moreover, as x decreases the perpendicular magnetic anisotropy increases and the Landau g factor exhibits a negative shift due to an increase in orbital momentum anisotropy. Our results will facilitate the design and exploration of new magnetic alloys with large magnetic anisotropy and desirable damping properties.PACS numbers: 75.78. Jp, 75.70.Tj, 75.50.Vv, 75.30.Gw + e-mail: hbzhao@fudan.edu.cn *e-mail: gxluep@wm.edu.[2] IntroductionUltrafast magnetization precessional switching in ferromagnets utilizing magnetic field pulses, spin polarized currents, and ultrafast laser pulses [1][2][3][4][5][6] is currently a popular topic due to its importance in magnetic information storage and spintronic applications. The uniform magnetization precession can be well modeled with Landau-Lifshitz-GilbertSlonczewski (LLGS) equation [7][8][9], where the Slonczewski torque term denotes the spin transfer torques (STTs), and the Gilbert damping parameter α determines the spin relaxation time [10] and is crucial for device performance [11][12][13][14]. The extrinsic Gilbert damping is due to nonlocal spin relaxation, such as spin pumping and magnon-magnon scattering, which can be tuned by artificial substrates, specially designed buffer and coverage layers [15][16][17][18][19][20][21], while the intrinsic Gilbert damping parameter α 0 is thought to arise from spin-orbit interaction (SOI) [22][23][24][25][26][27][28][29][30], and recently its quadratic dependence on SOI is demonstrated experimentally in FePtPd alloys [31].The α 0 describes the energy flow rate from spin to electronic orbital and phonon degrees of freedom through electron scattering, and has been studied in various theoretical models [22][23][24][25][26][27][28][29][30]. The breathing Fermi surface model [22] and torque-correlation model [23] based on first principle band structure calculations qualitatively match α 0 in soft magnetic alloys such as Fe, . Moreover, contributions to α 0 can be categorized based on intraband and interband transitions [23,26]. The damping rate from intraband transitions scales linearly with the electron relaxation time τ e and exhibits conductivity-like behavior. In contrast, the damping rate from the interband transition is proportional to the electron scattering rate 1/τ e , and consequently exhibits resistivity-like behavior. Therefore, the transition from conductivity-like to re...

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“…19,20 Similar relatively high values for the intrinsic Gilbert damping parameter were reported on continuous FePt films with lower magnetocrystalline anisotropy. [21][22][23] In summary, our here presented results show that coherent spin precession can be excited in a highly anisotropic, granular L1 0 FePt films using ultrashort light pulses of 100 fs. The high anisotropy fields up to more than 10 T found in the here investigated sample lead to FMR frequencies in the THz range.…”

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confidence: 99%

Laser induced spin precession in highly anisotropic granular L1 FePt

Becker

Mosendz

Weller

et al. 2014

Applied Physics Letters

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The dynamic magnetic properties of a highly anisotropic, granular L10 FePt thin film in magnetic fields up to 7 T are investigated using time-resolved magneto-optical Kerr effect measurements. We find that ultrashort laser pulses induce coherent spin precession in the granular FePt sample. Frequencies of spin precession up to over 400 GHz are observed, which are strongly field and temperature dependent. The high frequencies can be ascribed to the high value of the magnetocrystalline anisotropy constant Ku leading to large anisotropy fields Ha of up to 10.7 T at 170 K. A Gilbert damping parameter of α ∼ 0.1 was derived from the lifetimes of the oscillations.

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Fast magnetization precession observed in L1-FePt epitaxial thin film

Cited by 109 publications

References 22 publications

Nonlocal torque operators inab initiotheory of the Gilbert damping in random ferromagnetic alloys

Nonlocal torque operators inab initiotheory of the Gilbert damping in random ferromagnetic alloys

Role of antisite disorder on intrinsic Gilbert damping inL10FePt films

Laser induced spin precession in highly anisotropic granular L1 FePt

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