Showing papers by "Andrzej Maziewski published in 2007"

Magnetic and magnetoresistive properties of NiFe/Au/Co/Au multilayers with perpendicular anisotropy of Co layers

Abstract: The giant magnetoresistance (GMR), magnetization reversal, and domain structure of magnetron sputtered spin valve [NiFe/Au/Co/Au]N multilayers consisting of ferromagnetic layers with alternating in-plane (NiFe) and out-of-plane (Co) magnetic anisotropy has been investigated. For 0.4 3, the neighboring magnetic layers were observed to be coupled. This coupling is of magnetostatic origin. The effective coupling field, estimated from GMR dependencies, is of the order of 100 kA/m. Micromagnetic simulations confirm that the domain structure of Co layers influences the behavior of NiFe layers.

Influence of buffer layers on the texture and magnetic properties of Co/Pt multilayers with perpendicular anisotropy

Abstract: A study on the buffer layer dependence of film texture, surface roughness, and magnetization reversal mechanism in Co/Pt multilayers is presented. Four different buffers are used: (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 of film textures and surface morphologies. Samples with a Cu buffer (A) exhibit a low degree of film texture and are relatively rough. MOKE and MFM measurements on these films reveal that the magnetization reverses by the nucleation of numerous small domains due to a large dispersion of the activation energy barrier. Buffer layer structures where the first layer consists of Ta, on the other hand, result in (111)-textured Co/Pt multilayers with a more regular surface morphology. In these samples, magnetization reversal proceeds by fast domain wall movement.

Remote Teaching Experiments on Magnetic Domains in Thin Films

Abstract: We describe our experience in building a remote laboratory for teaching magnetic domains. Fulfilling the proposed on-line experiments, students can observe and study magnetization processes that are often difficult to explain with written material. It is proposed that networks of remotely accessible laboratories could be integrated in the Global Laboratory which could make research and education closer as well as disseminate knowledge and research results to a non-expert audience.

Magnetic phase diagram of ultrathin films

Abstract: By micromagnetic simulations and analytically we study the nonhomogeneous magnetization states of ultrathin films with perpendicular and in-plane anisotropy. Ground and metastable states are mapped onto a (K1,K2) phase diagram (where K1 and K2 are the first and second anisotropy constants, accordingly). It is shown that in the part of the phase diagram where K2<0, on increasing K1 or K2 the initial homogeneous in-plane magnetization distribution evolves in two sequential steps: (i) the appearance of two-phase metastable states with gradually decreasing in-plane domain fraction and (ii) a jump to a perpendicular domain state reaching 50% of the in-plane domain fraction. In the metastability area of the phase diagram, the possibility of topological frustrations in two-phase domain patterns is shown.

Magnetic properties of (Co/Au) N multilayers with various numbers of repetition N *

Abstract: Magnetization reversal processes and magnetic domain structures have been studied in multilayered systems consisting of magnetostatically coupled cobalt layers separated by non-magnetic/soft-magnetic ones. Observations of the domain structures have been performed at room temperature using Kerr microscopy and magnetic force microscopy technique. The studies have been focused on the key characteristics of magnetic hysteresis loops as well as the domain structures and domain periods in such systems.

GloLab: Creating a Global Internet-Accessible Laboratory

Abstract: We suggest the creation of a Global Web Laboratory (we call it GloLab) for scientific purposes and teaching experiments online. In this article, we discuss the main principles and problems of building such a global Internet-laboratory. An example of a current working laboratory for teaching magnetism experiments online is also discussed.

Image processing study of ultrathin cobalt domain structure evolution induced by overlayer structure

Abstract: Evolution of the domain structure (DS) in ultrathin cobalt films, deposited on sapphire substrate with the following structure: X\Au\Co(dCo nm thick layer or wedge)\X (dX nm thick layer or wedge perpendicular to Co wedge axis)\Au (where X is V or Mo) with perpendicular magnetization was investigated as a function of thickness dX. The study was performed using an optical polarizing microscope with CCD camera. Images of DS were recorded during various stages of magnetization reversal. A special software based on LabView® was employed for acquisition and processing of domain images. To analyze the observed domain structures, topology properties of magnetic images were determined. Preferential orientation of domain walls was found in ultrathin Co covered by Mo but not by V.

MFM STUDY OF DOMAIN STRUCTURE IN ULTRATHIN Co FILMS UNDER EXTERNAL MAGNETIC FIELD

Abstract: Ultrathin ferromagnetic films are of great interest for study magnetic properties due to their potential application as a high density storage media. In cobalt films (2-8 monolayers) epitaxially grown on Au(111) one can observe the spin reorientation transition (SRT) from out-of-plane magnetization for thin films to in-plane for thick films [1]. According to the theoretical predictions [2], the domain size drastically decreases approaching SRT. The domains became too small to be observed with magneto-optical Kerr effects. Magnetic force microscopy (MFM) is a well-established technique for imaging of small magnetic structures. In cooperation with external magnetic fields, MFM can be used to study the magnetization process with nanometer spatial resolution, e.g. it allows to measure a hysteresis curve even for an individual particle, which can be compared to ensemble measurements by magneto-optical techniques. The advantage of MFM-constructed hysteresis loops is an opportunity of understanding the origin of dispersion in switching fields. It is not easy to obtain good quality MFM images for ultrathin magnetic film due to the low magnetic signal and possible sample magnetization reversal during scanning [1]. In present work we study the magnetic domain structure of cobalt film near SRT and the influence of an external magnetic field on it by MFM.