Seedlayer interface enhanced magnetic anisotropy in CoPt (0002)-textured films (original) (raw)
Related papers
Effects of layering and magnetic annealing on the texture of CoPt films
Journal of Magnetism and Magnetic Materials, 2010
The effect of magnetic field annealing of magnetron sputtered CoPt alloy films and Co/Pt bilayers on the crystallographic texture of the obtained chemically ordered (L1 0 ) CoPt films is presented. In CoPt alloy films the main effect of the magnetic field is to suppress (1 1 1) growth in the early stages of L1 0 formation whereas the development of (0 0 1) versus (1 0 0) texture is related to chemical ordering strain. A higher degree of (0 0 1) texture is obtained by magnetically annealing Co/Pt bilayers since the initial (1 1 1) texture in the as-sputtered films is avoided and Co-Pt alloying occurs in the presence of the magnetic field.
Magnetic anisotropy and microstructure in sputtered CoPt(110) films
Catalysis Today, 2004
We compare structural and magnetic properties of CoPt films sputtered at 900 K on MgO(1 1 0) (with a Pt(1 1 0) buffer layer) and MgO(0 0 1) (with a Pt(0 0 1) buffer layer) substrates. We obtain a layer with the L1 0 tetragonal structure. The equiatomic L1 0 phase is a "natural" multilayer, which consists in a stacking along the [0 0 1] direction of pure Co and pure Pt monolayers. At this temperature, the growth of CoPt yields nearly single orientation epitaxial films: CoPt )[0 0 1]//MgO(1 1 0)[0 0 1] and CoPt(0 0 1)[1 1 0]//MgO(0 0 1)[1 1 0] as shown by transmission electron microscopy. On MgO substrates, the long-range chemical ordering is incomplete in contrast with the case of MgO(0 0 1) substrates, where long-range order is nearly perfect. Despite incomplete chemical ordering, a large in-plane magnetic anisotropy is present for the films grown on the MgO(1 1 0) substrate. This is interesting for the magnetic recording writing with a classical recording head and reading with a magnetoresistance head. The structural study of the CoPt films grown on MgO(1 1 0) has pointed out that three variants of the L1 0 phase coexist. The proportion of [1 0 0] and [0 1 0] variants, oriented at 45 • with the ordering growth direction, is much higher than the proportion of the [0 0 1] variant. In fact, the simulation of magnetization loops has shown that the easy magnetization axis is within the plane along the [1,−1,0] direction. This anisotropy is favored for the [1 0 0] and [0 1 0] variants. On MgO(0 0 1), the CoPt films grow as a single variant with the concentration modulation and the magnetic anisotropy along the growth direction.
IEEE Transactions on Magnetics, 2014
The effect of four different seed layers-Ru, Hf/Ru, Ru/Hf, and Hf on the magnetic properties of [Co 5/Pt 3 Å] multilayer (ML) stack with perpendicular magnetic anisotropy was investigated. The structural quality of the ML stacks was studied and correlated with the magnetic properties. Among the abovementioned seed layers, Ru promotes stronger fcc (111) texture in the ML due to less lattice mismatch (8% between Ru and Co) in Co/Pt MLs. As a result, higher anisotropy field (H K ∼ 17 kOe) and larger effective perpendicular anisotropy (K eff ∼ 1.2 × 10 7 erg/cm 3) were achieved for the MLs on Ru seed layer compared with other seed layers after annealing at 300°C for 30 min. The perpendicular magnetic anisotropy of the MLs is improved at higher annealing temperature up to 400°C for Ru and Hf/Ru seed layer. For the Co/Pt MLs on Ru, 1.3 × 10 7 erg/cm 3 perpendicular magnetic anisotropy was obtained even after annealing at 400°C. Detail investigations of postannealing stability of the ML films on different seed layers were also discussed. The magnetic properties and structural properties of the films on four different seed layers were characterized after rapid thermal annealing process at 300°C, 350°C, and 400°C for 30 min annealing duration. The high temperature endurance limit up to 400°C for 30 min of the Co/Pt MLs on Ru and Hf/Ru seed layers makes them compatible with the back-end-of-line process temperature.
Effect of nanostructuration on the magnetic properties of CoPt films
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2006
Ionic irradiation is used to magnetically pattern CoPt alloy films, using an appropriate mask to protect arrays of CoPt dots with a 1 mm 2 size, while the remainder of the film is exposed to ionic irradiation. Before irradiation, we obtain a layer with the Ll 0 tetragonal structure, ordered and with a strong perpendicular magnetic anisotropy energy in the growth direction. After irradiation, the unprotected regions become disordered and magnetically soft, whereas the protected regions remain magnetically hard. Spatially selective irradiation thus provides a spatial distribution of magnetic anisotropy and hence of the magnetization direction, perpendicular to plane in the ordered zones and in-plane in the disordered zones. The interest of ionic irradiation is that the film recovers its initial roughness after elimination of the mask which is promising for the data storage applications.
Seed-layer effect on the microstructure and magnetic properties of Co/Pd multilayers
Journal of Applied Physics, 2001
We have investigated Co/Pd multilayers deposited on either Ta or indium tin oxide ͑ITO͒ seed layers as a potential perpendicular recording media. We have examined the microstructural evolution of the films deposited on the two different types of seed layers and related it to the magnetic properties of the films. Ta underlayer produces a strong ͗111͘ fiber texture in the multilayer while ITO produces randomly oriented grains. Transmission electron microscopy reveals a microstructure of columnar grains separated by less dense material at the boundaries for the multilayers with an ITO underlayer. However, the less dense material is absent when using a Ta underlayer. The films exhibited strong perpendicular anisotropy and a higher coercivity of ϳ6800 Oe and squareness of ϳ0.99 are obtained for the films deposited on an ITO seed layer. The differences in the value of coercivity and squareness in the films can be correlated with the differences in the evolution of microstructures for different seed layers.
Micromagnetic properties of Co/Pt multilayers deposited on various buffer layers
MATERIALS SCIENCE-POLAND
A study on the buffer layer dependence of the film texture, surface roughness, and magnetization re-versal process in Co/Pt multilayers prepared by dc magnetron sputtering is presented. Oxidized Si(100) wafer was covered with four different buffers: (A) 10 nm Cu, (B) 5 nm Ta/10 nm Cu, (C) 5 nm Ta/10 nm Cu/5 nm Ta, and (D) 5 nm Ta/10 nm Cu/5 nm Ta/10 nm Cu. The growth of [2 nm Pt/0.5 nm Co]×5/2 nm Pt on top of these buffer layers results in a large variation in the fcc (111) Co/Pt texture and surface mor-phology. All films have the perpendicular magnetic anisotropy but magnetization reversal process, stud-ied by the magnetooptic Kerr effect (MOKE) and magnetic force spectroscopy (MFM), strongly depends on the buffer used. Observation of magnetic domains evolution under a MOKE microscope allows one to calculate from magnetization relaxation curves average dispersion of energy barriers of the thermal acti-vated magnetization switching process. The application of MFM in external magneti...
IEEE Transactions on Magnetics, 1996
4oNilPt multilayers were prepared by magnetron sputtering using Ar gas. Effects of Pt seedlayer and Ar sputtering pressure on magnetic and structural properties are investigated. Microstructures of multilayers were analysed using XRD and TEM. It was found that perpendicular magnetic anisotropy and coercivity increase with increasing either the thickness of Pt seedlayer or Ar pressure. The causes of increases in perpendicular anisotropy and coercivity are discussed in relation to the interface roughness, the curvature of layers and the columnar structures.
Anisotropy and interface structure in sputtered Co/Pt multilayers on Si
Journal of Magnetism and Magnetic Materials, 2003
The inter-relation between magnetic and structural properties of a series of Co/Pt sputtered multilayer films of constant period but differing number of repeats has been investigated. Independent measurements of the perpendicular anisotropy using vibrating sample, alternating gradient field and torque magnetometry were in excellent agreement. Previous measurements showing a large increase in effective anisotropy at about 15 bilayers were confirmed. Low and high angle X-ray scattering showed that the roughness of the interfaces was correlated in all samples and that the interfaces were sharp with no detectable interdiffusion. No systematic trends in roughness, in-plane correlation length or crystallographic texture could be detected with increasing bilayer repeat. The samples with higher perpendicular anisotropy had both lower Co and Pt thickness than the other samples, although this enhancement does not seem to be associated with the thickness variation. The interfaces in these samples had a fractal parameter h of unity, compared with 0.5 for the other samples. r
Physical Review B, 2009
The structure of Co/Pd multilayers has a strong effect on the localized anisotropy distribution within a film and on the resulting switching properties of nanostructures fabricated from identical material. By varying the underlying seed layer in sputtered films, the microstructure can be controlled from being highly ͑111͒ textured to having a random grain orientation. We find a strong correlation between the lateral homogeneity of grain orientations and the localized anisotropy distribution in the material. X-ray diffraction and reflectivity indicate that the interface is better defined and more uniform in the textured case, consistent with the presence of a strong interfacelike anisotropy.