Co/Pt and Co/Pd multilayers as magneto-optical recording materials

Hashimoto, Shunichi; Ochiai, Y.

doi:10.1016/s0304-8853(97)90031-7

Cited by 130 publications

(35 citation statements)

References 18 publications

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“…For the current work we rescaled these functions to match the material properties of a CoPd multilayer system [21,22]. These functions are shown in Fig.…”

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confidence: 99%

Role of Entropy in Domain Wall Motion in Thermal Gradients

et al. 2014

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Thermally driven domain wall (DW) motion caused solely by magnonic spin currents was forecast theoretically and has been measured recently in a magnetic insulator using magneto optical Kerr effect microscopy. We present an analytical calculation of the DW velocity as well as the Walker breakdown within the framework of the Landau Lifshitz Bloch equation of motion. The temperature gradient leads to a torque term acting on the magnetization where the DW is mainly driven by the temperature dependence of the exchange stiffness, or in a more general picture by the maximization of entropy. The existence of this entropic torque term does not rest on the angular momentum transfer from the magnonic spin current. Hence, even DWs in antiferromagnets or compensated ferrimagnets should move accordingly. We further argue that the entropic torque exceeds that of the magnonic spin current.Spin caloritronics is a new field of research focused on the combined transport of spin, charge, entropy, and energy in magnetic systems [1]. A good example for a spin caloritronic phenomenon is the spin Seebeck effect, the occurrence of spin currents or spin accumulation due to temperature gradients, which was discovered first in metallic ferromagnets [2]. Later on, this effect was also found in dilute magnetic semiconductors [3] and even in insulators [4]. In the latter case the existence of the spin Seebeck effect can only be explained by pure magnonic spin currents not resting on any charge transport.Spin caloritronic phenomena call for an exploitation in magnetic devices. In Ref.[5] the existence of thermally driven domain wall (DW) motion in a temperature gradient was demonstrated by computer simulations based either on the stochastic Landau-Lifshitz-Gilbert equation of motion for an atomistic spin model or-in a more micromagnetic picture-on the Landau-Lifshitz-Bloch (LLB) equation of motion for a thermally averaged spin polarization. The microscopic explanation for DW motion in temperature gradients rests on the diffusive motion of magnons from the hot end of a nanowire towards the colder end [6] and the transfer of angular momentum pushing the wall in the direction opposite to the magnonic spin current. Theoretical investigations based on these arguments give estimates for the DW velocity which can be achieved [7][8][9][10].In this work we will focus on a more thermodynamic point of view. At finite temperature T a DW is a thermodynamic object where the free energy ΔFðTÞ is the thermodynamic potential that is minimized. The free energy of the DW can be expressed as the difference between a magnetic system with DW minus the free energy of the same system without DW [11]. It is connected to the internal energy ΔU of the wall and its entropy ΔS via ΔF ¼ ΔU − TΔS. The temperature dependence of the different thermodynamic potentials are illustrated in Fig. 1 for a DW in a high anisotropic material. The calculations are from Ref. [11] for an atomistic spin model for FePt. However, the general features of a DW free energy do not depend on the ...

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“…For the current work we rescaled these functions to match the material properties of a CoPd multilayer system [21,22]. These functions are shown in Fig.…”

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confidence: 99%

Role of Entropy in Domain Wall Motion in Thermal Gradients

et al. 2014

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“…3(d). The resolution of the imaging can be estimated by taking into account the typical width of a domain wall in CoPt multilayer films (< 10 nm) [16,17], By fitting the measured intensity profile with a hyperbolic tangent of the form I = I 0 tanh[2(x − x 0 )/w] + I C [18], where x 0 is the center position of the domain wall, w is its width and, I 0 and I C are intensity offset values, we obtain a width of the domain boundary w ≈ 30 ± 10 nm in both directions. This value is of the order of the sample period (∼30 nm), and is thus limited by the maximal acceptance angle of the CCD camera.…”

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confidence: 99%

Magnetic imaging by x-ray holography using extended references

Duckworth¹,

Ogrin²,

Dhesi³

et al. 2011

Opt. Express

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Abstract:We demonstrate magnetic lensless imaging by Fourier transform holography using extended references. A narrow slit milled through an opaque gold mask is used as a holographic reference and magnetic contrast is obtained by x-ray magnetic circular dichroism. We present images of magnetic domains in a Co/Pt multilayer thin film with perpendicular magnetic anisotropy. This technique holds advantages over standard Fourier transform holography, where small holes are used to define the reference beam. An increased intensity through the extended reference reduces the counting time to record the farfield diffraction pattern. Additionally it was found that manufacturing narrow slits is less technologically demanding than the same procedure for holes. We achieve a spatial resolution of ∼30 nm, which was found to be limited by the sample period of the chosen experimental setup.

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“…The microscopic origin of both properties has been related to modifications of the magnetic properties of the 3d element resulting from the induced spin-polarization of Pt and hybridization of the electronic structure at the interfaces of the multilayers [3][4][5]. However, frequently, deposition and filmgrowth parameters may modify magnetic and magneto-optic features of samples in a way that is not always straightforward [1]. Ni/Pt multilayers present sharp interfaces with negligible amount of interdiffusion [6][7][8].…”

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confidence: 98%

“…1 Introduction Magnetic multilayers of the type 3d/Pt (3d = Fe, Co, Ni) are promising materials for perpendicular magneto-optic recording. Appealing features for such applications include the perpendicular magnetic anisotropy and the large Kerr rotation at the high energy range of the spectra (∼ 3-4 eV) [1,2]. The microscopic origin of both properties has been related to modifications of the magnetic properties of the 3d element resulting from the induced spin-polarization of Pt and hybridization of the electronic structure at the interfaces of the multilayers [3][4][5].…”

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confidence: 98%

Ni/Pt multilayers: growth and magneto‐optics

Papaioannou

Fumagalli

Angelakeris

et al. 2004

phys. stat. sol. (c)

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PACS 68.65. Ac, 78.20.Ls Ni/Pt multilayers were grown on glass, Si and polyimide substrates by e-beam evaporation under ultrahigh vacuum conditions. The deposition temperature was maintained just above room temperature, T dep ∼ 40 o C. X-ray diffraction experiments showed that the samples have almost as high quality as similar ones grown at higher temperatures. Atomic Force Microscopy images revealed small nanocrystallites with diameters in the range of 15-30 nm. The film roughness and the size distribution of the crystallites were found to be substrate-dependent. It is shown, however, that differences in the morphology among samples with the same Ni and Pt thickness grown on different substrates do not affect the magnetic and magnetooptic properties. The magneto-optic response is discussed with respect to the spin-polarization of Pt at interface proximity with Ni, recently observed in Ni/Pt multilayers. 1 Introduction Magnetic multilayers of the type 3d/Pt (3d = Fe, Co, Ni) are promising materials for perpendicular magneto-optic recording. Appealing features for such applications include the perpendicular magnetic anisotropy and the large Kerr rotation at the high energy range of the spectra (∼ 3-4 eV) [1,2]. The microscopic origin of both properties has been related to modifications of the magnetic properties of the 3d element resulting from the induced spin-polarization of Pt and hybridization of the electronic structure at the interfaces of the multilayers [3][4][5]. However, frequently, deposition and filmgrowth parameters may modify magnetic and magneto-optic features of samples in a way that is not always straightforward [1]. Ni/Pt multilayers present sharp interfaces with negligible amount of interdiffusion [6][7][8]. Thus, in this work we have selected Ni/Pt multilayers as a prototype system to compare the correlation between growth and magneto-optics on samples with identical individual layer thickness, prepared, however, on different substrates. We demonstrate that the substrate selection may modify the film morphology and, to a less extent, the layer quality, while, the magnetic and magneto-optic response remain practically unaltered.

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Co/Pt and Co/Pd multilayers as magneto-optical recording materials

Cited by 130 publications

References 18 publications

Role of Entropy in Domain Wall Motion in Thermal Gradients

Role of Entropy in Domain Wall Motion in Thermal Gradients

Magnetic imaging by x-ray holography using extended references

Ni/Pt multilayers: growth and magneto‐optics

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