Magnetotransport and magnetic properties of Co/Cu multilayers under the influence of In surfactant

Abstract

PACS 75.70.Cn The influence of In surfactant on the giant magnetoresistance (GMR) effect and magnetization processes has been investigated in Co/Cu thermally evaporated multilayers (MLs) with sublayer thicknesses of Co and Cu corresponding to the second antiferromagnetic maximum of interlayer coupling. Based on the Xray reflectivity (XRR) and atomic force microscopy (AFM) measurements it has been shown that In added in small amount at MLs interface leads to well ordered structures with small roughness (a few Å). This fact was reflected in magnetoresistivity values that were also larger for samples with In in comparison to pure Co/Cu multilayers. However, the magnetization hysteresis loops demonstrated the very small fraction of antiferromagnetic coupling in the investigated samples. These results indicate that the role of chemical roughness is not equivalent to the role of magnetic roughness. 1 Introduction GMR has recently received extensive attention due to its great potential in the field of magnetic sensors, high-density read-out heads and other magnetic storage technologies. One of the most promising candidate materials for devices reading/writing the magnetic information are Co/Cu multilayers [1], because of the very large GMR effect even at room temperature [2]. However, a wide variation of results for Co/Cu multilayers has been observed, indicating sensitivity of magnetic and transport properties to the preparation conditions [3,4]. The growth mode of films is determined by a combination of experimental parameters like the deposition rate and the orientation and temperature of the substrate, as well as by a number of fundamental energy parameters of the deposited material. The most important material parameter that is involved in the growth process is the adatom diffusion barrier. If, at given temperature and deposition flux the ratio of the adatom diffusion coefficient to the deposition flux is sufficiently large, deposited adatoms will not form stable nuclei and will only attach to steps. In this case the film growth process always proceeds in a smooth layer-by-layer way. However, additional barriers to interlayer transport are present, like the Ehrlich-Schwoebel barrier (ES) [5,6], that an adatom has to overcome to diffuse down a surface step. It is already known [7] that the presence of an ES barrier can lead to a growth instability, i.e. rough growth on an initially flat terrace. A high Ehrlich-Schwoebel barrier hinders the interlayer mass transport so that newly deposited adatoms cannot diffuse down when they have landed on top of an island. This process leads to the 3-dimensional growth of films.

Long‐chain acyl‐CoA synthetase 6 regulates lipid synthesis and mitochondrial oxidative capacity in human and rat skeletal muscle

“…These findings are supported by studies in rat brain, where it was observed to be involved in the incorporation of unsaturated fatty acids into phospholipids (Soupene et al 2010;Chen et al 2011). ACSL6 function was previously only described in neuronal cells (PC12) (Marszalek et al 2005) and in the brain from rats (Soupene et al 2010;Chen et al 2011). Consequently, we extend these initial findings using our rat model, where we further characterize the function of ACSL6 in skeletal muscle.…”

The effect of surfactants on the growth of Co/Cu multilayers

“…Application of a ML of Pb as a surfactant breaks down the coherent growth mode, disrupting the topographic correlation between the Co-Cu interfaces, and leads to creation of layers composed of small grains. Our atomic force microscope images taken for In surfactant [13] also demonstrated the small grain size in multilayers grown in the presence of a surfactant when compared to surfactant-free systems. This allows the conclusion that, in the present case also, the Bi and Pb surfactant segregation to the film surface results not only in smoother interfaces but also in diminishing the grain size.…”

AES Studies of Saturation in Surfactant Segregation Process in Co/Cu Multilayers

“…Figure 2 shows the change of the surfactant concentration as a function of Co/Cu bilayer number. The squares correspond to experimental results and the circles represent theoretical calculations using formulae (4) and (5). A and C were fitted parameters in these simulations.…”

“…The addition of a small amount of surfactant into the Co/Cu multilayered system significantly reduces the degree of interfacial roughness [3]. The results showing the correlation between structural and magnetic properties of surfactant mediated Co/Cu multilayers were published elsewhere [4,5]. Smoothing of the interfaces is a result of surfactant segregation to the surface of the Co/Cu multilayers.…”