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Andrzej Maziewski

Bio: Andrzej Maziewski is an academic researcher from University of Białystok. The author has contributed to research in topics: Magnetization & Magnetic anisotropy. The author has an hindex of 24, co-authored 236 publications receiving 2219 citations. Previous affiliations of Andrzej Maziewski include University of Warsaw & University of Paris-Sud.


Papers
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Journal ArticleDOI
TL;DR: In this article, the dependence of the magnetic anisotropy, magnetization reversal processes and magnetic domain patterns in Pt/Co(h)/Pt(1.1) ultra-thin ferromagnetic films have been studied, as a function of the Co layer thickness d (0.5⩽d➽3 ).

86 citations

Journal ArticleDOI
TL;DR: The silver overlayer thickness-driven magnetic reorientation from easy axis to easy plane generates a new type of 90 degrees magnetic wall for cobalt thicknesses between 1.3 and 1.8 nm.
Abstract: Complementary multiscale magneto-optical studies based on the polar Kerr effect are carried out on an ultrathin cobalt wedge covered with a silver wedge and subsequently with the Au thick layer. A few monolayers of Ag are found to have a substantial effect on magnetic anisotropy, the coercivity field, and Kerr rotation. The silver overlayer thickness-driven magnetic reorientation from easy axis to easy plane generates a new type of 90 degrees magnetic wall for cobalt thicknesses between 1.3 and 1.8 nm. The tuning of the wall width in a wide range is possible. Tailoring of the overlayer structure can be used for ultrathin film magnetic patterning.

82 citations

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TL;DR: The use of vector magnetometry is demonstrated to analyze the orientation of the magnetization in a cylindrically shaped microwire under the influence of an external magnetic field.
Abstract: We report a method of imaging of the magnetization reversal process using analysis of real-time images of magnetic domain structures in cylindrically shaped microwires. This method uses wide-field polarizing optical microscopy and is based on the magneto-optical Kerr effect (MOKE). The aperture diaphragm in MOKE microscope was used to control the incident angles of the light rays that reached the non-planar surface of the microwire and also determined the MOKE geometries. The movement of the non-central position of the hole in this diaphragm leads to a change in the orientation of the plane of incidence of the light along the perpendicular or the parallel direction to the axial direction of the wire. The visualization of the surface magnetic domain structures is obtained using polar and longitudinal MOKE geometries. The hysteresis loops were obtained by plotting the averaged image contrast as a function of the external magnetic field. The separation of the all-magnetization components is performed using different MOKE geometries in a microscope. We demonstrate the use of vector magnetometry to analyze the orientation of the magnetization in a cylindrically shaped microwire under the influence of an external magnetic field.

69 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical analysis of magnetization processes is proposed, starting from the model of a patchy inhomogeneous media with a realistic distribution of local coercivities, and the pertinent parameters for calculations are deduced from their experimental data using appropriate analytical expressions of the magnetic relaxation time and domain-wall velocity under a field.
Abstract: Magnetization-reversal processes in a ferromagnetic cobalt film structure (Au/Co/Au), with perpendicular anisotropy, were investigated by magneto-optical magnetometry and microscopy. In the considered ultrathin Co film, the magnetization reversal between the two Ising-spin equilibrium states is dominated by the domain-wall motion mechanism. We focused our studies on processes initiated from a given demagnetized state. Starting from a magnetically saturated state generated under a large field ${\mathrm{H}}_{\mathrm{S}}$, applied perpendicular to the film, this demagnetized state is created through magnetic aftereffects in a field ${\mathrm{H}}_{\mathrm{d}}$ antiparallel but smaller than ${\mathrm{H}}_{\mathrm{S}}$ and applied during a selected time. Direct (${\mathrm{R}}^{\mathrm{D}}$) and indirect (${\mathrm{R}}^{\mathrm{I}}$) magnetization processes are then studied from this state for application of the field parallel and antiparallel to ${\mathrm{H}}_{\mathrm{d}}$, respectively. The dynamics of the magnetization reversal is much faster for the ${\mathrm{R}}^{\mathrm{I}}$ process since it is initiated from a quasihomogeneous 'Swiss cheese' domain state with small nonreversed regions. The magnetic accommodation phenomenon is studied, and a domain-shape memory effect evidenced. A theoretical analysis of the dynamics of magnetization processes is proposed, starting from the model of a patchy inhomogeneous media with a realistic distribution of local coercivities. The pertinent parameters for calculations are deduced from our experimental data using appropriate analytical expressions of the magnetic relaxation time and domain-wall velocity under a field. Computer simulations using these parameters reproduce well the time evolution of the magnetic domain pattern and different magnetization curves both for ${\mathrm{R}}^{\mathrm{D}}$ and ${\mathrm{R}}^{\mathrm{I}}$ magnetization processes.

66 citations

Journal ArticleDOI
TL;DR: In this paper, two-dimensional diagrams of magnetic and magneto-optical properties have been derived and the out-of-plane magnetic anisotropy states with enhanced magnetooptical effects were evidenced for specific (${d}_{\mathrm{Co}}$, $F$) values.
Abstract: Magnetization orientation in Ga${}^{+}$-irradiated Pt/Co(${d}_{\mathrm{Co}}$)/Pt ultrathin films can be changed in a controlled way by adjusting the ion fluence, $F$. Two-dimensional (${d}_{\mathrm{Co}}$, $F$) diagrams of magnetic and magneto-optical properties have been derived. Distinct out-of-plane magnetic anisotropy states with enhanced magneto-optical effects were evidenced for specific (${d}_{\mathrm{Co}}$, $F$) values. This rich behavior originates from two competing mechanisms: intermixing of Co and Pt atoms at the interfaces and the formation of ordered CoPt alloy phases with high magnetic anisotropy. The irradiation-induced effects open novel routes for both tailoring thin-film magnetic and magneto-optical properties and patterning of magnetic nanostructures.

63 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the progress in this field of laser manipulation of magnetic order in a systematic way and show that the polarization of light plays an essential role in the manipulation of the magnetic moments at the femtosecond time scale.
Abstract: The interaction of subpicosecond laser pulses with magnetically ordered materials has developed into a fascinating research topic in modern magnetism. From the discovery of subpicosecond demagnetization over a decade ago to the recent demonstration of magnetization reversal by a single 40 fs laser pulse, the manipulation of magnetic order by ultrashort laser pulses has become a fundamentally challenging topic with a potentially high impact for future spintronics, data storage and manipulation, and quantum computation. Understanding the underlying mechanisms implies understanding the interaction of photons with charges, spins, and lattice, and the angular momentum transfer between them. This paper will review the progress in this field of laser manipulation of magnetic order in a systematic way. Starting with a historical introduction, the interaction of light with magnetically ordered matter is discussed. By investigating metals, semiconductors, and dielectrics, the roles of nearly free electrons, charge redistributions, and spin-orbit and spin-lattice interactions can partly be separated, and effects due to heating can be distinguished from those that are not. It will be shown that there is a fundamental distinction between processes that involve the actual absorption of photons and those that do not. It turns out that for the latter, the polarization of light plays an essential role in the manipulation of the magnetic moments at the femtosecond time scale. Thus, circularly and linearly polarized pulses are shown to act as strong transient magnetic field pulses originating from the nonabsorptive inverse Faraday and inverse Cotton-Mouton effects, respectively. The recent progress in the understanding of magneto-optical effects on the femtosecond time scale together with the mentioned inverse, optomagnetic effects promises a bright future for this field of ultrafast optical manipulation of magnetic order or femtomagnetism.

1,449 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive survey of experimental studies on the magnetic anisotropy in metallic multilayers containing Fe, Co or Ni is presented and commented on, with the help of some dedicated experimental studies.
Abstract: Ferromagnetic materials exhibit intrinsic `easy' and `hard' directions of the magnetization. This magnetic anisotropy is, from both a technological and fundamental viewpoint one of the most important properties of magnetic materials. The magnetic anisotropy in metallic magnetic multilayers forms the subject of this review article. As individual layers in a multilayer stack become thinner, the role of interfaces and surfaces may dominate that of the bulk: this is the case in many magnetic multilayers, where a perpendicular interface contribution to the magnetic anisotropy is capable of rotating the easy magnetization direction from in the film plane to perpendicular to the film plane. In this review, we show that the (in-plane) volume and (perpendicular) interface contribution to the magnetic anisotropy have been separated into terms related to mechanical stresses, crystallographic structure and the planar shape of the films. In addition, the effect of roughness, often inherent to the deposition techniques used, has been addressed theoretically. Several techniques to prepare multilayers and to characterize their growth as well as methods to determine the magnetic anisotropy are discussed. A comprehensive survey of experimental studies on the perpendicular magnetic anisotropy in metallic multilayers containing Fe, Co or Ni is presented and commented on. Two major subjects of this review are the extrinsic effects of strain, roughness and interdiffusion and the intrinsic effect of the crystallographic orientation on the magnetic anisotropy. Both effects are investigated with the help of some dedicated experimental studies. The results of the orientational dependence studies are compared with ab initio calculations. Finally, the perpendicular surface anisotropy and the in-plane step anisotropy are discussed.

1,099 citations

Journal ArticleDOI
TL;DR: This topical review addresses materials with a periodic modulation of magnetic parameters that give rise to artificially tailored band structures and allow unprecedented control of spin waves in microand nanostructured ferromagnetic materials.
Abstract: Research efforts addressing spin waves (magnons) in micro- and nanostructured ferromagnetic materials have increased tremendously in recent years. Corresponding experimental and theoretical work in magnonics faces significant challenges in that spin-wave dispersion relations are highly anisotropic and different magnetic states might be realized via, for example, the magnetic field history. At the same time, these features offer novel opportunities for wave control in solids going beyond photonics and plasmonics. In this topical review we address materials with a periodic modulation of magnetic parameters that give rise to artificially tailored band structures and allow unprecedented control of spin waves. In particular, we discuss recent achievements and perspectives of reconfigurable magnonic devices for which band structures can be reprogrammed during operation. Such characteristics might be useful for multifunctional microwave and logic devices operating over a broad frequency regime on either the macro- or nanoscale.

535 citations

Journal ArticleDOI
TL;DR: In this article, different approaches for the realization of static, reconfigurable, and dynamic magnonic crystals are presented along with a variety of novel wave phenomena discovered in these crystals.
Abstract: Magnons—the quanta of spin waves—propagating in magnetic materials with wavelengths at the nanometer-scale and carrying information in the form of an angular momentum, can be used as data carriers in next-generation, nano-sized low-loss information processing systems. In this respect, artificial magnetic materials with properties periodically varied in space, known as magnonic crystals, are especially promising for controlling and manipulating the magnon currents. In this article, different approaches for the realization of static, reconfigurable, and dynamic magnonic crystals are presented along with a variety of novel wave phenomena discovered in these crystals. Special attention is devoted to the utilization of magnonic crystals for processing of analog and digital information. Magnonic crystals for data processing 2

353 citations