Deposition of thick Co-rich CoPtP films with high energy product for magnetic microelectromechanical applications (original) (raw)
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Influence of temperature on the magnetic properties of electroplated Co-rich Co–Pt thick films
Journal of Micromechanics and Microengineering, 2014
In this paper, the magnetic properties of 10 µm thick Co-rich Co-Pt films (∼80:20 atomic ratio) hard magnetic films electroplated on silicon substrates are characterized at temperatures from 300 to 1000 K. With an increase in temperature up to 500 K, the coercivity and remanence of the films both decrease rapidly, dropping to only 10% of their respective as-deposited values. Above 500 K, the coercivity and remanence continue declining but at a slower rate, reaching nearly zero at 1000 K. Conversely, the saturation magnetization reduces by only 15% at 800 K and 40% at 1000 K from the as-deposited value. In addition to these measurements at elevated temperature measurements, thermal cycling tests are performed to examine the influence of various thermal exposures. Cycles up to 500 K are shown to have little impact on the film morphology but notably reduce the layer adhesion. Most importantly, a thermal cycle to just 400 K is shown to essentially destroy the hard magnetic properties. Because of these temperature sensitivities, Co-rich Co-Pt films may be significantly limited for end applications.
Growth rate dependence of the extrinsic magnetic properties of electrodeposited CoPt films
Journal of Magnetism and Magnetic Materials, 2010
The magnetic properties and the magnetization process of electrodeposited thick films of Co-rich CoPt alloys are studied with particular emphasis on the effects of growth rate, controlled by varying the plating current density, and of lateral confinement, analyzing patterned micro-cylinders. We find that varying the plating current density has virtually no effect on the composition of the samples, and hence on the intrinsic magnetic properties, a substantial increase of both coercivity and squareness is obtained when the current is raised. The films are fine-grained, oriented polycrystals with typical grain sizes in the range 50-150 nm, depending on the growth rate. The complex magnetization process is studied in detail by Magnetic Force Microscopy and shown to be governed by interaction domains. It is shown that further improvement of the squareness can be obtained by exploiting the lateral confinement in patterned samples.
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.
CoPt and FePt thin films for high density recording media
Journal of Applied Physics, 2000
Granular CoPt/C and FePt/C films, consisting of nanoparticles of the highly anisotropic fct CoPt (FePt) phase embedded in a carbon matrix, were made by co-sputtering from pure Co 5 oPt 50 (Fe 5 oPt 5 o) and C targets using a tandem deposition mode. The as-made films showed a disordered face centered cubic (fcc) structure, which was magnetically soft and had low coercivity. Magnetic hardening occurred after heat treatment at elevated temperatures, which led to increase in coercivity with values up to 15 kOe. The hardening originated from the transformation of the fcc phase to a highly anisotropic face centered tetragonal phase (fct) with anisotropy K > 10 7 erg/cm 3 . Transmission electron microscopy studies showed FePt particles embedded in C matrix with a particle size increasing from below 5 nm in the as-made state to 15 nm in the fully annealed state. These results are very promising and make these materials potential candidates for high-density magnetic recording. G.M. Chow et al. (eds.), Nanostructured Films and Coatings, 171-176.
Microstructure investigations of hcp phase CoPt thin films with high coercivity
Journal of Applied Physics, 2014
CoPt films have been grown in the past with a high anisotropy in L1 1 or L1 0 phase, and a high coercivity is observed only in L1 0 CoPt films. Recently. we have grown CoPt films which exhibited a high coercivity without exhibiting an ordered phase. In this study, high resolution transmission electron microscopy (HRTEM) investigations have been carried out to understand the strong thickness and deposition pressure dependent magnetic properties.
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.
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.
Journal of Applied Physics, 2007
We present structural and magnetic properties of three sets of structures: as-deposited CoPt films cosputtered at 900 K on MgO͑110͒ substrates with a Pt͑110͒ buffer layer and CoPt films deposited by molecular beam epitaxy directly on MgO͑110͒ substrates at 900 K, as prepared and annealed at 900 K. All layers have the L1 0 tetragonal structure. The chemical long-range ordering for the as-deposited CoPt films is incomplete in contrast with the annealed CoPt films, where long-range order is the highest. The structural study of these CoPt films grown on MgO͑110͒ has pointed out that three variants of the L1 0 phase coexist. The proportion of x and y variants, with the concentration modulation along a vector oriented at 45°with respect to the growth direction, is higher than the proportion of the z variant with the concentration modulation within the plane. The magnetic study shows an in-plane easy magnetization axis with a large magnetic anisotropy. This is interesting for the magnetic recording media with classical longitudinal writing and reading heads. The simulation of the magnetization loops confirms that the easy magnetization axis is within the plane and along the ͓110͔ direction, favored by the dominant x and y variants.
Journal of Magnetism and Magnetic Materials, 2005
Co-rich, Co-Pt alloy films containing $20 at% Pt and small amounts of P, with thickness from 125 to 1000 nm have been galvanostatically (constant current) grown by electroplating onto Cu seed layers with strong (1 1 1) orientation. The influence of deposition current density (cd ¼ 10-50 mA/cm 2 ) and film thickness on their growth morphology, structural and magnetic properties have been investigated. When electrodeposited on Cu(1 1 1), Co-Pt(P) films develop a microstructure consisting of a disordered hexagonal-closed-packed (hcp) matrix with {0 0 0 1} preferential orientation. At low cd, a small amount of simple cubic L1 2 phase was detected, which disappears altogether by increasing cd to 50 mA/cm 2 . The plated films show saturation magnetization in the range 775-832 kA/m (778-832 emu/cm 3 ), large perpendicular magnetic anisotropy up to 1.02 MJ/m 3 (1.02 Â 10 7 erg/cm 3 ), and coercivity up to 486 kA/m (6.1 kOe) in the out-of-plane direction. The perpendicular anisotropy was found to originate predominantly from the high magnetocrystalline anisotropy of the hcp phase of Co-Pt(P) with c-axis perpendicular to the substrate. r