[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Journal of Physics Condensed Matter: Preface

IN view of the interest attaching to the vaporisation and diffusion of solids, the following observations may be worthy of record.

The Diffusion of Solids

Current-induced effective magnetic fields can provide efficient ways of electrically manipulating the magnetization of ultrathin magnetic heterostructures. Two effects, known as the Rashba spin orbit field and the spin Hall spin torque, have been reported to be responsible for the generation of the effective field. However, a quantitative understanding of the effective field, including its direction with respect to the current flow, is lacking. Here we describe vector measurements of the current-induced effective field in Ta|CoFeB|MgO heterostructrures. The effective field exhibits a significant dependence on the Ta and CoFeB layer thicknesses. In particular, a 1 nm thickness variation of the Ta layer can change the magnitude of the effective field by nearly two orders of magnitude. Moreover, its sign changes when the Ta layer thickness is reduced, indicating that there are two competing effects contributing to it. Our results illustrate that the presence of atomically thin metals can profoundly change the landscape for controlling magnetic moments in magnetic heterostructures electrically.

▲Current-induced effective field vector in Ta│CoFeB│MgO

In this work, high power impulse magnetron sputtering (HiPIMS) was used for the first time to grow Fe4N films. The Fe4N phase can only be formed when N is precisely at 20 at. %. Therefore, it is expected that the Fe4N phase can be obtained by optimization of growth parameters such as N2 gas flow, substrate temperature (Ts) etc. We varied process parameters and found that under optimized conditions single phase Fe4N phase can be obtained at Ts=675 K. Depth profile of Fe4N sample was studied using secondary ion mass spectroscopy and it was found that substantial inter-diffusion takes place between the substrate-film interface when Ts=675 K. This prohibits accurate estimation of saturation magnetization (Ms) by bulk magnetization methods. By using surface sensitive soft x-ray magnetic circular dichroism (MCD) we found that Ms is close to its theoretical value of about 2.5 µB/Fe atom. These are first ever MCD measurements performed on the soft x-ray absorption beamline BL-01 at Indus-2 synchrotron radiation source.

Preparation and characterization of Fe4N thin film deposited by high power impulse magnetron sputtering

Grazing incidence neutron reflectometry provides an opportunity to measure the depth profile of a thin film sample with a resolution <1 nm, in a non-destructive way. In this way the diffusion across the interfaces can also be measured. In addition, neutrons have contrast among the isotopes, making it feasible to measure the self-diffusion. In the present work, the isotope multilayers of [FeN/57FeN]10 and [FeN/Fe15N]10 were prepared using magnetron sputtering and self-diffusion of Fe and N was investigated. It was found that N diffusion is slower compared to Fe and does not follow the atomic size dependence.

Fe and N diffusion in nitrogen-rich FeN measured using neutron reflectometry

Thick films of Bi2Sr2CaCu2Ox superconducting at 84 K have been prepared on polycrystalline MgO substrates. The effect of heat treatment on phases formed at various stages of the film preparation is studied. Investigations show that a thin layer at the top is highly oriented while the bulk of the 212 phase material beneath it consists of randomly oriented grains. This appears to be the main reason for the low critical current densities obtained in practice.

Phase formation and crystallization in Bi-Sr-Ca-Cu-O thick films

Study of magnetic zigzag domain walls and magnetization reversal process in polycrystalline cobalt thin films: Effect of thickness and crystallographic texturing

Sputtered Fe/Nb multilayers were prepared with Nb thicknesses dNb of 35 A and with Fe thicknesses dFe of 35 A and sputtered Fe/Nb/Fe trilayers was deposited with Nb thicknesses dNb in the range 50 A and with Fe thicknesses dFe in the range 120 A, respectively using high power impulse magnetron sputtering technique. X-ray reflectivity (XRR) measured patterns revealed the high quality of the film structure with a low surface and interface roughness. Nb thin films synthesized with Nb thicknesses dNb in the range 150-700 A using conventional direct-current magnetron sputtering (CMS) have been compared with those made by high power impulse magnetron sputtering (HIPIMS) operated at the same average power by means of XRR. The obtained XRR patterns were fitted using the Parratt32 software. It was observed that films grown by HIPIMS method have a higher density and interface roughness than that grown by the CMS method. It was also observed that the deposition rate is increasing with the increase of deposition power; it shows linear behavior with deposition power.

Mukul Gupta

Papers

Preparation and characterization of Fe4N thin film deposited by high power impulse magnetron sputtering

Fe and N diffusion in nitrogen-rich FeN measured using neutron reflectometry

Phase formation and crystallization in Bi-Sr-Ca-Cu-O thick films

Study of magnetic zigzag domain walls and magnetization reversal process in polycrystalline cobalt thin films: Effect of thickness and crystallographic texturing

Deposition of Fe/Nb multilayers and Fe/Nb/Fe trilayers using HIPIMS: XRR measurements for interface diffusion study