Time filter

Source Type

Swierczek J.,42 Technology | Mydlarz T.,International Laboratory of High Magnetic Fields and Low Temperatures
Journal of Alloys and Compounds | Year: 2011

Microstructure, revealed by transmission electron microscopy and conventional Mössbauer spectroscopy, magnetization versus magnetizing field induction and temperature and isothermal magnetic entropy changes in the as-quenched and subjected to annealing at Ta1 = 723 K for 2 or 3 h and at Ta2 = 743 K for 2.5 h of Fe90Zr7B 3 amorphous alloy are studied. In the as-quenched state the medium range ordered regions are observed. The annealing at Ta1 leads to early stages of crystallization and nanograins with different diameter embedded in amorphous matrix are formed. At the Curie point of the amorphous phase they are magnetically decoupled and behave like superparamagnetic particles. The Curie point of the residual amorphous phase shifts towards higher temperature as compared to the as-quenched state due to the Invar like effect. The peak of the isothermal magnetic entropy changes appears at the Curie temperature of the main amorphous phase. Their values at the maximum applied field of 0.75 T equals to 0.32 J/kg K-1 in the as-quenched alloy and remain almost unchanged after early stages of nanocrystallization. After the annealing at Ta2 the peak of the entropy changes distinctly decreases. Such behavior is ascribed to the biphasic character of the sample. The main amorphous phase and ordered one, which in some circumstances can be treated as an assembly of superparamagnetic particles, contribute to the total magnetic entropy changes. © 2011 Elsevier B.V. All rights reserved.


Cwik J.,International Laboratory of High Magnetic Fields and Low Temperatures
Journal of Solid State Chemistry | Year: 2014

This paper presents a review and results of comparative study of the influence of Gd on some physical properties of (R0.9R′ 0.1)1-xGdxCo2 solid solutions with R=Dy, Ho and R′=Er, Ho and x varied from 0.05 to 0.15. Powder X-ray diffraction analysis performed at room temperature revealed that all studied solid solutions solidify with the formation of a Laves-phase MgCu 2-type structure (space group Fd-3m). The magnetization behavior and the magnetic transition are analyzed in terms of the Landau theory. The studies of magnetic properties and heat capacity showed that a relatively small Gd addition significantly increases TC of the compounds. The maximum percentage increase in TC, namely, ~43% was observed for (Ho 0.9Er0.1)1-xGdxCo2. However, the highest temperature was noted for the (Dy0.9Ho 0.1)0.85Gd0.15Co2 solid solution; it is TC=183.4 K. Below the ordering temperature, all samples are ferrimagnetically ordered; at high temperatures, they are Curie-Weiss paramagnets. Moreover, a small Gd addition eliminates the field-induced magnetic transition near TC and, as consequence, transforms the nature of magnetic transition from the first- to second-order. The magnetocaloric effect has been estimated in terms of both isothermal magnetic entropy and adiabatic temperature changes. The highest adiabatic temperature change ΔT ad=3 K and highest isothermal entropy change ΔS mag=12.1 J/kg K were observed for (Ho0.9Er 0.1)0.95Gd0.05Co2 at ~90 K in magnetic fields of 2 T and 3 T, respectively. A decrease in the entropy change has been observed with increasing Gd content in all studied samples. The smallest values of ΔSmag were observed for the (Dy 0.9Ho0.1)1-xGdxCo2 solid solutions. Under an external field change of from 0 to 3 T, the maximum entropy change for (Dy0.9Ho0.1)1-xGdxCo 2 compounds decreases from 6.9 at x=0.05-4.3 J/kg K at x=0.15. The refrigerant capacity for all solid solutions (with 0.05≤x≤0.15) is reported. The effect of increasing Gd content in the solid solutions on their magnetic and magnetocaloric properties is discussed. © 2013 Elsevier Inc.


Cwik J.,International Laboratory of High Magnetic Fields and Low Temperatures | Kolchugina N.,RAS Institute of Metallurgy | Nenkov K.,Leibniz Institute for Solid State and Materials Research
Journal of Alloys and Compounds | Year: 2013

Structural, magnetic and magnetocaloric properties and heat capacity of polycrystalline Dy1-xHoxCo2 (0.1 ≤ x ≤ 0.5) solid solutions were investigated experimentally using by X-ray diffraction, magnetic and heat capacity measurements; the Landau theory was applied also to clarify peculiarities of magnetic phase transition in the compounds. X-ray diffraction patterns taken at room temperature exhibit the existence of the C15 cubic Laves phase structure for all samples under study. The lattice parameter decreased from 0.7186 for x = 0.1-0.7179 nm for x = 0.5 and the Curie temperature TC decreases from 130 to 109 K as the Ho content increases to x = 0.5. The isothermal entropy change -ΔS mag was calculated according to magnetic measurements using thermodynamic Maxwell's relation. A large entropy change has been observed for all Ho concentrations. Under an external field change from 0 to 3 T, the maximum entropy change fluctuates within 9 J/kg K. The maximum ΔTad value varies within 3 and 2 K for a magnetic field change of 2 and 1 T, respectively. The effect of increasing Ho amount in the Dy1- xHoxCo2 solid solutions on their magnetic and magnetocaloric properties is discussed. © 2013 Elsevier B.V. All rights reserved.


Nizhankovsky V.I.,International Laboratory of High Magnetic Fields and Low Temperatures | Tsebro V.I.,RAS Lebedev Physical Institute
Physics-Uspekhi | Year: 2013

V I Nizhankovsky, V I Tsebro shared their views on how the International Laboratory (IL) of High Magnetic Fields and Low Temperatures was established and evolved. C Bazan, who headed the International Laboratory from 1968 until his retirement in 1985, informed that the idea of establishing it belonged to Polish researchers. Polish physicist, professor Roman Ingarden made significant contributions in establishing the international laboratory by organizing the Low Temperatures Laboratory of the Polish Academy of Sciences in Wroclaw. The choice of location for the future International Laboratory was predetermined and certain favorable factors facilitated anchoring the IL in Wroclaw. The main efforts of the IL staff members focused on the development of methods for generating high magnetic fields with the aid of water-cooled Bitter magnets and on designing magnets of various powers as the backbone of the experimental base of the laboratory.


Nizhankovskii V.I.,International Laboratory of High Magnetic Fields and Low Temperatures
European Physical Journal B | Year: 2013

The remanent magnetization Mr on easy-axis antiferromagnetic single crystal K2FeCl5·H2O is investigated. The sign of the remanent magnetization depends on the direction of the applied magnetic field H; if it is perpendicular to the easy axis of antiferromagnet then the sign of the remanent magnetization is positive, i.e. it coincides with the sign of the magnetic field in which the sample was cooled down below TN. Instead, if the magnetic field is directed along the easy axis then the sign of the remanent magnetization is negative and its absolute value is three orders of magnitude larger than usual magnetization M(TN,H). © 2013 EDP Sciences, Società Italiana di Fisica, Springer-Verlag.


Cwik J.,International Laboratory of High Magnetic Fields and Low Temperatures
Physica Status Solidi (B) Basic Research | Year: 2013

The magnetic and magnetocaloric properties of polycrystalline (Dy0.9Ho0.1)1-xGdxCo2 (0.0≤x≤0.15) solid solutions were investigated experimentally using magnetic measurements; the Landau theory was also applied to clarify peculiarities of the magnetic phase transition in the compounds. X-ray diffraction patterns taken at room temperature exhibit the existence of the C15 cubic Laves phase structure for all samples under study. The lattice parameter increased from 0.7186 for x=0.0 to 0.7194nm for x=0.15 and the Curie temperature TC increases from 130 to 183K as the Gd content increases to x=0.15. The isothermal entropy change ΔSmag was calculated according to magnetic measurements using the thermodynamic Maxwell's relation. A decrease in entropy change with the increase of Gd content has been observed. Under an external field change of from 0 to 3T, the maximum entropy change decreased from 8.1 for x=0.0 to 4.3Jkg-1K-1 for x=0.15. The effect of increasing the Gd amount in the (Dy0.9Ho0.1)1-xGdxCo2 solid solutions on their magnetic and magnetocaloric properties is discussed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Cwik J.,International Laboratory of High Magnetic Fields and Low Temperatures
Journal of Alloys and Compounds | Year: 2013

Magnetic and magnetocaloric properties of polycrystalline (Dy 0.9Er0.1)1-xGdxCo2 (0.0 6 x 6 0.25) solid solutions were investigated experimentally using magnetic measurements. The magnetization behavior and magnetic transition are analyzed in terms of Landau theory. Powder X-ray diffraction analysis performed at room temperature showed that all (Dy0.9Er0.1) 1-xGdxCo2 (0.0 6 x 0.25) solid solutions are C15 cubic Laves phase with the MgCu2-type structure. The lattice parameter increases from 0.7187 for Dy0.9Er0.1Co 2 to 0.7204 nm for (Dy0.9Er0.1) 0.75Gd0.25Co2. In this case, the Curie temperature increases from 128 K to 215 K for. At higher temperatures, all solid solutions are Curie-Weiss paramagnets. The isothermal entropy change -δSmag was calculated using magnetic measurements data and thermodynamic Maxwell's relation. A decrease in the entropy change has been observed with increasing Gd content. Under an external field change of from 0 to 3 T, the maximum entropy change for these compounds decreases from 8.5 at x = 0.0 to 3.1 J/kg K at x = 0.25. The refrigerant capacity of the (Dy 0.9Er0.1)1-xGdxCo2 solid solutions (with 0.0 6 x 6 0.25) is presented. The effect of increasing Gd content in the (Dy0.9Er0.1)1-xGd xCo2 solid solutions on their magnetic and magnetocaloric properties is discussed. © 2013 Elsevier B.V. All rights reserved.


Nizhankovskii V.I.,International Laboratory of High Magnetic Fields and Low Temperatures
Journal of Superconductivity and Novel Magnetism | Year: 2012

Spontaneous magnetization of an eutectic In 0.15 Ga 0.85-sapphire interface is discovered. Magnetic moment is directed from an insulator to a metal, its density corresponds to 1.8×10 18 m -2 localized spin-1/2 states. © Springer Science+Business Media, LLC 2011.


Nizhankovskii V.I.,International Laboratory of High Magnetic Fields and Low Temperatures
European Physical Journal B | Year: 2010

Magnetostriction and magnetization of MnF 2 samples are measured at several temperatures from T = 4.2 to 70 K in fields up to 14 T directed along and perpendicular to the easy-axis direction [001]. Obtained results confirm the thermodynamic description of magnetostriction proposed earlier. © 2010 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.


Nizhankovskii V.I.,International Laboratory of High Magnetic Fields and Low Temperatures
Physics Research International | Year: 2011

Change of the chemical potential of electrons in a GaAs-Al x Ga 1-x As heterojunction was measured in magnetic fields up to 6.5 T at several temperatures from 2.17 to 12.3K. A thermodynamic equation of state of two-dimensional electron gas well describes the experimental results. Copyright © 2011 V. I. Nizhankovskii.

Loading International Laboratory of High Magnetic Fields and Low Temperatures collaborators
Loading International Laboratory of High Magnetic Fields and Low Temperatures collaborators