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    ABSTRACT: The recently developed ferromagnetic shape memory alloys (FSMA) exhibit large field induced strains thereby rendering new potentials for application in transducers, actuators and other novel devices. Magnetically controlled strain in FSMA is based on the reorientation of the twin structure of martensite under applied magnetic field. A detailed study of both martensitic and magnetic domain structure is presented for oriented single-crystalline bulk and texturized powdered samples embedded in polymer matrix, and polycrystalline bulk and rapidly quenched ribbon alloys. Optical microscopy including magneto-optical indicator film technique was employed alongside with X-ray and AFM/MFM studies for the characterization of the coexisting structural and magnetic domains. It is shown that only 180° magnetic domains exist in twin plates because martensite possesses uniaxial magnetic anisotropy having magnetization vector M oriented along easy c-axes at angles of ±45° with respect to the twin boundaries. Due to magnetostatic coupling the 180° magnetic domains of neighbouring twins cooperate with each other forming continuous macrodomains running through the whole crystallite or single crystal sample and changing the direction of M by ±90° in a zigzag fashion at each intersection of the twin boundary.
    Full-text · Dataset · Sep 2014
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    Dataset: RAMS 2009

    Full-text · Dataset · Sep 2014
  • T. Breczko · J. Tamuliene
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    ABSTRACT: The work is devoted to the Heusler alloys as a candidate for applications in spintronics. On the basis of experimental studies the electronic structures of these alloys by computer simulations were carried out to explain the structural and electronic properties of the Ni2MnGa and Co 2MnGa compounds by using state-of-the-art computational ab-initio methods. The total energy calculations for the cubic structures, band structure and their nature and magnetizability of the compounds are investigated. The obtained results explained the dependence of the magnetic properties of the alloys on the geometrical structure as well influence of Co and Ni atoms.
    No preview · Article · Jan 2014 · Materials Physics and Mechanics
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    ABSTRACT: The results of the computer simulations of certain electronic properties of the austenite phase of Ni-Mn-Ga alloy are presents. Cluster approach was used and both self-consistent and density functional methods were exploited
    Full-text · Article · Jan 2013 · Materials Science Forum
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    Krzysztof Kuś · Teodor Breczko
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    ABSTRACT: The stress-free thermal cycling with help of a differential scanning calorimeter (DSC) is executed through the transformation range of a fully annealed Ni-Ti alloy sample, continuously observing the variations in the calorimetric profiles and related thermal parameters. The influence of two different cooling rates right after annealing on the transformation properties is extra and separately examined. It is found that as the thermal cycle number increases, the transformation sequence changes into a two-stage behaviour on cooling, and the first visible symptoms related to the appearance of intermediate R-phase occur after 10 th full cycle. Apart from a progressive decrease of the critical temperatures, there is no DSC evidence for the two-stage reaction on heating within the whole thermal cycling test. As a result of the higher cooling rate after annealing, somewhat higher transformation temperatures are measured for the Ni-Ti alloy.
    Full-text · Article · Jan 2012 · Materials Physics and Mechanics
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    ABSTRACT: The paper presents results of the computer simulations and experimental investigation of physical properties of Ni-Mn-Ga alloy. The study was performed using atomic force microscope. The chemical composition of researched specimens causes generation of martensite and austenite phases. Computer simulations are devoted to austenite phase
    Full-text · Article · Mar 2010 · Materials Physics and Mechanics
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    Krzysztof Kus · Teodor Breczko
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    ABSTRACT: The variations in thermal transformation properties due to annealing within the temperature range from 400°C to 600°C were studied for the near equiatomic Ni-Ti shape memory alloy by the Differential Scanning Calorimetry (DSC) measurements. There was a critical temperature (about 600ºC), where the specimens demonstrated remarkably different transformation courses. There were also noticeable changes in transformation temperatures and heats depending on the annealing temperature. It is thought that the alterations of the mi-crostructure in the Ni-Ti alloy during annealing are responsible for such behavior.
    Full-text · Article · Jan 2010 · Materials Physics and Mechanics
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    Adam Fraczyk · Teodor Breczko
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    ABSTRACT: Crystallization of amorphous metallic alloy Fe95Si5 (at. %) was investigated using X-ray diffraction measurements performed in-situ during isothermal annealing. Fe95Si5 rib- bons, prepared by melt-spinning, have been analyzed by differential scanning calorimetry (DSC). Their nanostructural evolution has been studied by combining heat treatments with conventional X-ray diffraction. The objective of the experiment was to determine changes in the structural parameters during crystallization of the examined alloy. The crystalline diame- ter and the lattice constant of the crystallizing phase were used as parameters to evaluate structural changes in the material.
    Full-text · Article · Jan 2010 · Materials Physics and Mechanics
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    ABSTRACT: The martensitic and magnetic domain structures of polycrystalline and single-crystal samples of ferromagnetic Heusler alloys of the Ni-Mn-Ga and Co-Ni-Ga families have been revealed and studied using optical microscopy. The main mechanisms of formation and interaction of 90° and 180° magnetic domains have been described.
    Full-text · Article · Jan 2010 · Physics of the Solid State
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    ABSTRACT: A method of localized polarization-optical measurement of dielectric hysteresis loop parameters on microscopical areas of ferroelectric samples combined with simultaneous observation of their domain structure is proposed. A sensitive two-beam differential polarization-optical hysteresisgraph is built for performing the experiments. Examples are given of the study of slow domain structure relaxation processes and dielectric hysteresis curves of lead germanate Pb5Ge3O11.
    Full-text · Article · Jul 2009 · Physics of the Solid State
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    Full-text · Article · Apr 2009 · Reviews on Advanced Materials Science
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    ABSTRACT: The recently developed ferromagnetic shape memory alloys (FSMA) exhibit large field induced strains thereby rendering new potentials for application in transducers, actuators and other novel devices. Magnetically controlled strain in FSMA is based on the reorientation of the twin structure of martensite under applied magnetic field. A detailed study of both martensitic and magnetic domain structure is presented for oriented single-crystalline bulk and texturized pow-dered samples embedded in polymer matrix, and polycrystalline bulk and rapidly quenched ribbon alloys. Optical microscopy including magneto-optical indicator film technique was employed along-side with X-ray and AFM/MFM studies for the characterization of the coexisting structural and magnetic domains. It is shown that only 180° magnetic domains exist in twin plates because mar-tensite possesses uniaxial magnetic anisotropy having magnetization vector M oriented along easy c-axes at angles of ±45° with respect to the twin boundaries. Due to magnetostatic coupling the 180° magnetic domains of neighbouring twins cooperate with each other forming continuous macrodomains running through the whole crystallite or single crystal sample and changing the direction of M by ±90° in a zigzag fashion at each intersection of the twin boundary.
    Full-text · Article · Apr 2009 · Reviews on advanced materials science
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    ABSTRACT: In the Cu-Mn-Al Heusler alloy ternary system the martensitic transformation may pro-ceed in solid solutions having concentration nonuniformities related to small coherent particles forming during the degradation of the high temperature phase and having no spontaneous mar-tensitic transformation on cooling. These particles may have a size well below the critical size of martensite nucleation. In the present work we study the temperature dependence of the structure and magnetic properties of Cu-Mn-Al in the temperature interval including the phase transition. Forward (cooling) and reverse (heating) structural transformations were studied directly by optical microscopy and illustrated by movies showing the motion and transformation pathways of multiple martensite interfaces. Simultaneous temperature measurements of the AC magnetic susceptibil-ity gave a possibility to estimate the volume changes of high-and low-temperature phases during the transformation necessary for modelling the behaviour of this type of alloys.
    Full-text · Article · Jan 2009
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    ABSTRACT: This article reports an computer simulations of physical properties of Heusler NiMnGa alloy. Computer simulation are devoted to austenite phase. The chemical composition of researched specimens causes generation martesite and austenite phases.
    Full-text · Article · Jul 2008 · Proceedings of SPIE - The International Society for Optical Engineering
  • Alexander I. Melker · Teodor Breczko

    No preview · Article · Apr 2007 · Proceedings of SPIE - The International Society for Optical Engineering
  • Teodor Breczko · Andrzej Lempaszek
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    ABSTRACT: Functional materials, of which an example is ferroelectric, ferroelastic monocrystal of molybdate (III) gadolinium (VI), are often used in the micro-motor operators (micro-servo motors) working in changeable environment conditions. Most frequently this change refers to temperature. That is why the important practical problem is the precise measurement of the value of piezoelectric tensor elements in dependence on the temperature of a particular monocrystal. In the presented article for this kind of measurements, the use of X-ray diffractometer has been shown. The advantage of the method presented is that, apart from precise dependence measurement between the temperature of a monocrystal and the value of piezoelectric tensor elements, it enables synchronous measurement of the value of thermal expansion tensor elements for a monocrystal.
    No preview · Article · Apr 2007 · Proceedings of SPIE - The International Society for Optical Engineering
  • Teodor Breczko
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    ABSTRACT: The functional properties of crystals have been described by the thermodynamics potential of a crystal. This potential usually is presented as matrix, the elements of which represent physical properties of crystals. Using the partial derivatives we can obtain some physical properties of crystals. In the experimental part of article the results of study of some functional properties of a ferroelastic monocrystal of molybdate (III) gadolinium (VI) are presented.
    No preview · Article · Apr 2007 · Proceedings of SPIE - The International Society for Optical Engineering
  • Teodor Breczko · Miroslaw Bramowicz
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    ABSTRACT: In this paper we present results of the investigation of polycrystalline Ni52,2Mn21,3Ga26,5 alloy before and after homogenisation at 1173K processed for different time intervals. We investigated the influence of duration of homogenisation on kinetics of reversible martensitic transformation (RMT). In order to present changes of kinetics of RMT, thermal hysteresis was determined based on calorimetric (DSC) investigation. Our results suggested that thermal annealing at 1173K caused plastic deformation of crystal lattice in the investigated alloy.
    No preview · Article · Apr 2007 · Proceedings of SPIE - The International Society for Optical Engineering
  • Teodor Breczko · Janusz Szczepanek
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    ABSTRACT: In the article the results of diffractometric, calorimetric research as well as the chemical constitution have been presented. The research was carried out on the samples made of a thin amorphous tape made with the melt-spinning method from the alloy revealing the memory Ti50Ni25Cu25 effect. The samples were subjected to annealing at different parameters of holding in temperature. After the heat treatment, the response of martensite transformation and formed crystal structures has been observed. The X-ray microstructural tests showed forming so-called outer (top) "free" layer of lamellar precipitation of the high level of coherence.
    No preview · Article · Apr 2007 · Proceedings of SPIE - The International Society for Optical Engineering
  • Teodor Breczko · Adam Fronczyk · Krzysztof Kus
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    ABSTRACT: From literature data it can be concluded that physical properties of the amorphous alloys depend on the type of chemical composition. Further modification physical properties of these alloys can be achieved by a proper heat treatment process and structural changes of material. In the paper the experimental results of the Fe97.45Si2.55 amorphous alloy are presented with major attention to determine an influence of isothermal annealing (various temperatures and time periods) on the changes of selected structural parameters in the process of primary crystallization. Hence, lattice constant of crystallized phase, alpha, root-mean-square micro-strains, RMS, and coherent block sizes, D, were established as the structural parameters. These structural characteristics were determined using an X-ray analysis. As a mechanical parameter, we considered a micro-hardness of the heat treated alloy.
    No preview · Article · Apr 2005 · Proceedings of SPIE - The International Society for Optical Engineering

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