Perpendicular magnetic anisotropy in CoxPt1 − x alloy films

Maret, M.; Cadeville, M.C.; Staiger, W.; Beaurepaire, E.; Poinsot, R.; Herr, A.

doi:10.1016/0040-6090(95)07049-4

Cited by 40 publications

(25 citation statements)

References 6 publications

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“…The different magnetometry techniques employed to study the Co-Pt granular films reveal the presence of PMA in all the samples in the series. Similar PMA behavior has been observed in several Co-Pt multilayer systems [21][22][23][24], Co x Pt 1−x alloy films [11,[25][26][27], and nanopatterned Co-Pt systems [28], and is correlated to the structure of the alloy present in the sample. For instance, CoPt alloys with composition close to Co 0.5 Pt 0.5 may have a disordered fcc structure or a chemically ordered tetragonal structure L1 0 .…”

Section: Discussionsupporting

confidence: 49%

“…This results from the crystallization of Co-Pt alloys in the chemically ordered L1 0 phase, which, in bulk form, has a very high magnetocrystalline anisotropy [20]. In addition, many Co-Pt multilayer systems [21][22][23][24], Co x Pt 1−x alloy films [11,[25][26][27], and nanopatterned Co-Pt systems [28] show perpendicular magnetic anisotropy (PMA): a property that favors the easy axis of magnetization along the film normal direction. This PMA property is interesting for applications in spintronic nanodevices, for example, in ultrahigh-density magnetic storage, fast memory applications, and nanosensors [29,30].…”

Section: Introductionmentioning

confidence: 99%

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Structural and magnetic properties of granular Co-Pt multilayers with perpendicular magnetic anisotropy

et al. 2014

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We present a study of granular Co-Pt multilayers by means of high-resolution transmission electron microscopy (HRTEM), extended x-ray absorption fine structure (EXAFS), SQUID-based magnetic measurements, anomalous Hall effect (AHE), and x-ray magnetic circular dichroism (XMCD). We describe these granular films as composed of particles with a pure cobalt core surrounded by an alloyed Co-Pt interface, embedded in a Pt matrix. The alloy between the Co and Pt in these granular films, prepared by room temperature sputter deposition, results from interdiffusion of the atoms. The presence of this alloy gives rise to a high perpendicular magnetic anisotropy (PMA) in the granular films, as consequence of the anisotropy of the orbital moment in the Co atoms in the alloy, and comparable to that of highly-ordered CoPt L1 0 alloy films. Their magnetic properties are those of ferromagnetically coupled particles, whose coupling is strongly temperature dependent: at low temperatures, the granular sample is ferromagnetic with a high coercive field; at intermediate temperatures the granular film behaves as an amorphous asperomagnet, with a coupling between the grains mediated by the polarized Pt, and at high temperatures, the sample has a superparamagnetic behavior. The coupling/decoupling between the grains in our Co-Pt granular films can be tailored by variation of the amount of Pt in the samples.

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Section: Discussionsupporting

confidence: 49%

Section: Introductionmentioning

confidence: 99%

Structural and magnetic properties of granular Co-Pt multilayers with perpendicular magnetic anisotropy

et al. 2014

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“…by Co-Pt intermixing. A similar dependence of PMA on crystal structure was observed in Co x Pt 1-x alloys 24 .…”

supporting

confidence: 62%

Effect of substrate temperature on the magnetic properties of epitaxial sputter-grown Co/Pt

Mihai

Whiteside

Canwell

et al. 2013

Applied Physics Letters

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Epitaxial Co/Pt films have been deposited by dc-magnetron sputtering onto heated C-plane sapphire substrates. X-ray diffraction, the residual resistivity and transmission electron microscopy indicate that the Co/Pt films are highly ordered on the atomic scale. The coercive field and the perpendicular magnetic anisotropy increase as the substrate temperature is increased from 100-250C during deposition of the Co/Pt. Measurement of the domain wall creep velocity as a function of applied magnetic field yields the domain wall pinning energy, which scales with the coercive field. Evidence for an enhanced creep velocity in highly ordered epitaxial Co/Pt is found. 2Co/Pt multilayers have been studied for a number of years 1,2 , initially because of their potential as magneto-optical recording media 3 . Their attractive properties include perpendicular magnetic anisotropy (PMA) and a large polar magneto-optic Kerr effect (MOKE) at short wavelengths 4 . More recently Co/Pt has become an interesting system for the study of the physics of domain walls (DWs) [5][6][7][8] , and spin torque [9][10][11][12][13] . The PMA leads to the formation of narrow, nanometre-scale DWs, and the large polar Kerr effect is convenient for measuring the DW motion. However, DWs tend to pin at grain boundaries in the polycrystalline Co/Pt that is typically used in these studies 9 , and this is an issue not only for investigations of the fundamental physics of DWs but also for future devices which may depend upon reliable DW motion, such as racetrack memory 14 . Epitaxial Co/Pt, in which the density of grain boundaries is minimised, could provide a solution to this problem. Ideally, however, the method of multilayer deposition should be compliant with industrial processes.Sputtering is a convenient, cost-effective technique for thin film deposition and may be used to grow films epitaxially if a single crystal substrate is heated to an appropriate temperature.In order to obtain PMA in epitaxial Co/Pt, the films are required to grow in the (111)-orientation 15 , and (111) texture was first seen in sputtered Co/Pt in 1993 16 . While there have been studies of Co/Pt superlattices 17 and Pt/Co/Pt sandwiches 18 grown by sputtering, there has been no optimisation of sputtered epitaxial Co/Pt (111) for DW devices. Here we show how the substrate temperature may be used to tune the magnetic properties of epitaxial Co/Pt grown on sapphire.First, the growth of Pt on C-plane (0001) sapphire was optimised. A 60 nm Pt film was deposited at various substrate temperatures in the range 400-700C. High angle X-ray scans all had a clear peak between 39.5 and 40, indicating (111) structure (see Figure 1). The 3 peak was largest and the satellite peaks were best defined for a deposition temperature of 500C indicating that at this temperature the crystal quality of the film was highest. It was also found that overnight annealing of the sapphire substrate at 700 C improved film quality. X-ray reflectivity curves were measured from Pt films deposited both after a s...

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“…This very anisotropic chemical order is accompanied by a strong magnetic anisotropy and a tetragonality (c/a < 1). The pronounced anisotropic properties of CoPt are at the core of the present renewed interest in this system [21,22,23]. In thin films, L1 0 -CoPt alloys display, in addition to a high magnetic anisotropy, a magnetisation that is perpendicular to the film surface , thus making such films good candidates for magnetooptical-storage devices [24].…”

Section: Introductionmentioning

confidence: 99%

Saddle-point energies and Monte Carlo simulation of the long-range order relaxation in CoPt

Allalen

Bouzar²,

Mehaddene³

2005

Eur. Phys. J. B

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Abstract. We present atomic-scale computer simulations in equiatomic L10-CoPt where Molecular Dynamics and Monte Carlo techniques have both been applied to study the vacancy-atom exchange and kinetics relaxation. The atomic potential is determined using a Tight-Binding formalism within the Second-Moment Approximation. It is used to evaluate the different saddle-point energies involved in a vacancy-atom exchange between nearest-neighbour sites. The potential and the saddle-point energies have been used to simulate the relaxation of the long-range order in CoPt using a Monte Carlo technique. A vacancy migration energy of 0.73 ± 0.15 eV and an order-disorder transition temperature of 935 K have been found. PACS

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Perpendicular magnetic anisotropy in CoxPt1 − x alloy films

Cited by 40 publications

References 6 publications

Structural and magnetic properties of granular Co-Pt multilayers with perpendicular magnetic anisotropy

Structural and magnetic properties of granular Co-Pt multilayers with perpendicular magnetic anisotropy

Effect of substrate temperature on the magnetic properties of epitaxial sputter-grown Co/Pt

Saddle-point energies and Monte Carlo simulation of the long-range order relaxation in CoPt

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