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154 results on '"Kiss, L.F."'

12. Transition to superparamagnetism in a Cr-containing FINEMET-type alloy

Author

Franco, V., Conde, C.F., Conde, A., Kiss, L.F., and Kemeny, T.

Subjects
Hysteresis -- Analysis, Magnetic materials -- Testing, Business, Electronics, Electronics and electrical industries
Abstract

The transition from a ferromagnetic to a superparamagnetic regime has been studied in a Cr-containing FINEMET-type alloy. Cr enhances the thermal stability of the alloy against nanocrystallization and reduces the Curie temperature of the remaining amorphous phase. Above room temperature, the temperature dependent hysteresis loop of a nanocrystalline sample can be described by a model of interacting superparamagnetic particles. The temperature dependence of the apparent magnetic moment of the particles obtained from the fittings is interpreted in an extended version of the model. Index Terms--Hysteresis, magnetic materials, magnetization processes.

Published
2002

13. Dipole-dipole interaction in superparamagnetic nanocrystalline Fe63.5Cr10Si13.5B9Cu1Nb3

Author

Franco, V., Conde, C.F., Conde, A., Kiss, L.F., Kaptas, D., Kemeny, T., and Vincze, I.

Subjects
Nanotechnology -- Research, Physics
Abstract

Various techniques have been used to investigate Cr-substituted Finemet-type nanocrystalline alloy (Fe63.5Cr10Si13.5B9Cu1Nb3). The Cr addition boosts the thermal stability of the amorphous phase against nanocrystallization and produces a slightly reduced mean grain size of the Fe3Si-type nanophase.

Published
2001

28. Magnetic structure of the magnetoelectric material Ca$_{2}$CoSi$_{2}$O$_{7}$

Author

Sazonov, A., Hutanu, V., Meven, M., Roth, G., Murakawa, H., Tokura, Y., Guduru, V.K., Peters, L.C.J.M., Zeitler, U., Kiss, L.F., Szaller, D., Náfrádi, B., and Kézsmárki, I.

Subjects
Soft Condensed Matter & Nanomaterials (HFML), ddc:530, Correlated Electron Systems / High Field Magnet Laboratory (HFML), GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

Detailed investigation of Ca$_{2}$CoSi$_{2}$O$_{7}$ was performed in its low-temperature magnetoelectric state combining neutron diffraction with magnetization measurements on single crystals. The crystal and magnetic structures well below the antiferromagnetic transition temperature of TN≈5.7 K were determined using neutron diffraction. Neutron diffraction data imply no structural phase transition from 10 K down to 2.5 K and are well described within the orthorhombic space group P21212 with a 3×3×1 supercell compared with the high-temperature unmodulated state (tetragonal space group P¯421m). We found that in zero magnetic field the magnetic space group is P212′12′ with antiferromagnetic order along the [100] or [010] axes for two types of 90∘ twin domains, while neighboring spins along the [001] axis are ordered ferromagnetically. A noncollinear spin arrangement due to small canting within the ab plane is allowed by symmetry and leads to the existence of the tiny spontaneous magnetization below TN. The ordered moment with a magnitude of about 2.8 μB/Co$_{2}$+ at 2.5 K lies in the ab plane. Distinct differences between the magnetic structure of Ca$_{2}$CoSi$_{2}$O$_{7}$ as compared to those of Ba$_{2}$CoGe$_{2}$O$_{7}$ and Sr$_{2}$CoSi$_{2}$O$_{7}$ are discussed.

Published
2017

33. Influence of Mn on the magnetocaloric effect of nanoperm-type alloys

Author

Caballero-Flores, R., Franco, V., Conde, A., and Kiss, L.F.

Subjects
Iron alloys -- Magnetic properties, Iron alloys -- Thermal properties, Iron alloys -- Electric properties, Magnetization -- Analysis, Manganese -- Magnetic properties, Manganese -- Thermal properties, Manganese -- Electric properties, Physics
Abstract

The effect of the Mn content on the magnetocaloric response of ribbon-shaped amorphous samples of [Fe.sub.80-x][Mn.sub.x][B.sub.20] is analyzed by obtaining the temperature and field dependence of the magnetic entropy change from magnetization curves. A linear relationship between the maximum entropy change and the average magnetic moment per transition metal atom is described.

Published
2010

34. Magnetocaloric response of [Fe.sub.75][Nb.sub.10][B.sub.15] powders partially amorphized by ball milling

Author

Ipus, J.J., Blazquez, J.S., Franco, V., Conde, A., and Kiss, L.F.

Subjects
Iron compounds -- Properties, Iron compounds -- Analysis, Magnetochemistry -- Analysis, Physics
Abstract

The magnetocaloric response of mechanically alloyed [Fe.sub.75][Nb.sub.10][B.sub.15] powders is analyzed for samples with different amorphous and nanocrystal volume fractions. Curie temperature of the amorphous phase has increased as the amorphous fraction has increased due to its progressive enrichment and the field dependence of the peak magnetic entropy change is explained by the multiphase character of the studied samples.

Published
2009

35. Correlation between microstructure and temperature dependence of magnetic properties in [Fe.sub.60][Co.sub.18][(Nb,Zr).sub.6][B.sub.15][Cu.sub.1] alloy series

Author

Blazquez, J.S., Franco, V., Conde, C.F., Conde, A., Ferenc, J., Kulik, T., and Kiss, L.F.

Subjects
Cobalt -- Magnetic properties, Cobalt -- Electric properties, Iron alloys -- Magnetic properties, Iron alloys -- Thermal properties, Iron alloys -- Electric properties, Magnetization -- Analysis, Niobium -- Electric properties, Niobium -- Magnetic properties, Zirconium -- Magnetic properties, Zirconium -- Electric properties, Physics
Abstract

The temperature dependence of magnetic properties of nanocrystalline [Fe.sub.60][Co.sub.18][Cu.sub.1][B.sub.15][Nb.sub.6-x][Zr.sub.x] (x=0, 3, 6) alloys is studied at different stages of devitrification. Thermal dependence of the exchange stiffness constant is obtained from the measurement of specific magnetization and coercivity as a function of crystalline fraction and temperature for the three studied alloys.

Published
2009

36. Influence of the demagnetization field on the determination of the magnetocaloric effect from magnetization curves

Author

Caballero-Flores, R., Franco, Conde, A., and Kiss, L.F.

Subjects
Entropy (Physics) -- Analysis, Magnetic fields -- Analysis, Magnetization -- Analysis, Phase transformations (Statistical physics) -- Analysis, Physics
Abstract

The effect of the demagnetizing factor (N) on the magnetic entropy change ([DELTA][S.sub.M]) curves is analyzed for materials with a second order phase transition. The universal curve for the magnetocaloric effect is used for eliminating the effect of N and comparing the [DELTA][S.sub.M](T) curves for samples with different shapes.

Published
2009

37. Magnetocaloric response of FeCrB amorphous alloys: predicting the magnetic entropy change from the Arrott-Noakes equation of state

Author

Franco, V., Conde, A., and Kiss, L.F.

Subjects
Iron compounds -- Chemical properties, Iron compounds -- Magnetic properties, Chromium compounds -- Chemical properties, Chromium compounds -- Magnetic properties, Physics
Abstract

The magnetic entropy change in [Fe.sub.92-x][Cr.sub.8][B.sub.x] (x = 12, 15) amorphous alloys and the thermal and field dependences of the magnetic entropy change curves are analyzed by using the Arrott-Noakes equation of state. The studies have shown that the parameters in the equation of state have predicted the field and temperature dependences of the magnetic entropy change curves in a broad temperature range around the Curie temperature.

Published
2008

38. Magnetic permeability of [(FeCoGe).sub.88][Zr.sub.6][B.sub.5][Cu.sub.1] alloys: thermal stability in a wide temperature range

Author

Blazquez, J.S., Conde, C.F., Franco, V., Conde, A., and Kiss, L.F.

Subjects
Cobalt -- Thermal properties, Cobalt -- Magnetic properties, Copper alloys -- Structure, Copper alloys -- Thermal properties, Copper alloys -- Magnetic properties, Germanium -- Thermal properties, Germanium -- Magnetic properties, Magnetism -- Analysis, Physics
Abstract

The thermal dependence of the initial permeability ([mu]) from room temperature up to 1000 K is analyzed as a function of microstructure for two Ge and Co containing Nanoperm alloys. The studies have shown that as the nanocrystallization has progressed, the room temperature [mu] has decreased but high temperature one has increased, thus leading to an improvement of its thermal stability.

Published
2008

39. A constant magnetocaloric response in FeMoCuB amorphous alloys with different Fe/B ratios

Author

Franco, V., Conde, C.F., Blazquez, J.S., Conde, A., Svec, P., Janickovic, D., and Kiss, L.F.

Subjects
Metallic glasses -- Magnetic properties, Metallic glasses -- Thermal properties, Entropy (Physics) -- Analysis, Magnetic fields -- Analysis, Physics
Abstract

The magnetocaloric effect of FeMoCuB amorphous alloys is analyzed. The analysis has shown that controlling the Fe/B ratio in soft magnetic FeMoCuB amorphous alloys with low B content has helped in tuning the temperature at which the maximum magnetocaloric effect takes place, without changing the magnitude of the magnetic entropy change.

Published
2007

40. Change in soft magnetic properties of Fe-based metallic glasses during hydrogen absorption and desorption

Author

Novak, L., Lovas, A., and Kiss, L.F.

Subjects
Iron compounds -- Structure, Iron compounds -- Magnetic properties, Hydrogenation -- Analysis, Stress relaxation (Materials) -- Structure, Stress relaxation (Materials) -- Electric properties, Chemistry, Education, Science and technology
Abstract

The stress level can be altered in soft magnetic amorphous alloys by hydrogen absorption. The resulting changes in the soft magnetic parameters are reversible or irreversible, depending on the chemical composition and some of these effects are demonstrated in Fe-B, Fe-W-B, and Fe-V-B glassy ribbons, in which various magnetic parameters are measured mainly during hydrogen desorption.

Published
2005

42. Soft magnetic properties of high-temperature nanocrystalline alloys: permeability and magnetoimpedance

Author

Blazquez, J.S., Franco, V., Conde, A., and Kiss, L.F.

Subjects
Alloys -- Magnetic properties, Nanolithography, Physics
Abstract

The soft magnetic properties like permeability and magnetoimpedance of high-temperature nanocrystalline alloys are studied. It is seen that the results on coercivity are in line with the other results, which can be attributed to the domain wall stabilization phenomenon.

Published
2003

43. Magnetic phase diagrams of amorphous (Ni100-xFex)-metalloid alloys: The key role of the electronic density of states at the Fermi level for the onset of magnetic order.

Author

Kiss, L.F. and Bakonyi, I.

Subjects
*SEMIMETALS, *TRANSITION metals, *FERROMAGNETIC-paramagnetic transitions
Abstract

There have been extended studies on the appearance of ferromagnetism in transition-metal–metalloid (MD) glasses. In particular, the paramagnetic (PM) to ferromagnetic (FM) transition has been investigated on numerous (Ni 100-x Fe x )-MD alloys upon the introduction of Fe where MD can represent a combination of various metalloid elements, while keeping the metal/metalloid ratio constant. It has been reported that adding a sufficient amount of Fe to a Pauli PM Ni-MD alloy matrix first induces a spin-glass (SG) state at low temperatures which goes over to a PM state at higher temperatures. Beyond a certain Fe content, x c , the SG state transforms to a FM state upon increasing the temperature. By plotting the characteristic transition temperatures as a function of the Fe content, a magnetic phase diagram can be constructed for each Ni-Fe-MD system which has a multicritical point (MCP) at x c . By using the reported magnetic phase diagrams of various Ni-Fe-MD alloy systems, it is shown that the critical Fe content, x c scales inversely with the density of states at the Fermi level, N ( E F ), of the parent Ni-MD matrix. This means that the higher the N ( E F ), the lower the critical Fe content to induce ferromagnetism in the Ni-MD matrix. This is then discussed in terms of the Stoner enhancement factor, S , which characterizes the tendency of the matrix to become ferromagnetic. [ABSTRACT FROM AUTHOR]

Published
2017
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46. Temperature dependence of giant magnetoresistance and magnetic properties in electrodeposited Co-Cu/Cu multilayers: The role of superparamagnetic regions

Author

Peter, L., Rolik, Z., Kiss, L.F., Toth, J., Weihnacht, V., Schneider, C.M., Bakonyi, I., and Publica

Subjects
ddc:530
Abstract

We have shown recently that both the magnetization and the magnetoresistance of electrodeposited Co-Cu Cu multilayers can be decomposed by assuming the presence of both ferromagnetic (FM) and superparamagnetic (SPM) regions in the magnetic layers. In the present work, for two selected samples, one with a large SPM and another one with a large FM contribution to the giant magnetoresistance, low temperature magnetic and magnetoresistance measurements were performed in order to reveal the evolution of the FM and SPM terms with temperature. The average apparent magnetic moment of the SPM regions deduced from the two sets of data showed a good agreement. The role of electrochemical processes in the formation of the SPM regions is discussed. An attempt has also been made to elaborate on some models for the spatial distribution of the constituent elements (Co and Cu) leading to the occurrence of SPM regions. The results are discussed also in the framework of interacting SPM regions.

Published
2006

47. Giant magnetoresistance in electrodeposited multilayer films

Author

Bakonyi, I., Peter, L., Weihnacht, V., Toth, J., Kiss, L.F., Schneider, C.M., and Publica

Abstract

When preparing an alternating sequence of magnetic (Co or Ni) and non-magnetic (Cu) layers by electrodeposition using the two-pulse plating technique, a dissolution of the less-noble magnetic Co and Ni atoms can take place during the deposition of the more noble and non-magnetic Cu atoms. This process results in changes of the actual sublayer thicknesses with respect to the nominal values and can also cause some chemical intermixing at the magnetic/non-magnetic interfaces. As a consequence, superparamagnetic (SPM) regions with "loose magnetic moments" can form as has been demonstrated for electrodeposited Ni-Cu/Cu multilayers. We have also shown recently for electrodeposited Co-Cu/Cu multilayers that if some fraction of the magnetic layers exhibits SPM behaviour then the observed giant magnetoresistance (GMR) can be quantitatively decomposed into a ferromagnetic (FM) and a SPM contribution. In this paper, the results of a similar GMR decomposition study are presented fo r two electrodeposited Co-Cu/Cu multilayers. In the multilayer with strongly non-saturated magnetoresistance curves, the dominant GMR term was due to SPM regions, whereas in the other multilayer for which the magnetoresistance is mostly saturated in magnetic fields around 1 to 2 kOe, the FM contribution to the GMR is much larger. At the same time, magnetic measurements on the first multilayer sample have also revealed the presence of a large SPM contribution to the magnetization.

Published
2005

48. Slow relaxation of low temperature vortex phases in Bi_{2}Sr_{2}CaCu_{2}O_{8}

Author

Portier, F., Kriza, G., Sas, B., Kiss, L.F., Pethes, I., Vad, K., Keszei, B., Williams, F.I.B., Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
Superconductivity (cond-mat.supr-con), [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Condensed Matter::Superconductivity, Condensed Matter - Superconductivity, FOS: Physical sciences, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph]
Abstract

Nonlinear transport in the low temperature vortex glass state of single crystal Bi_{2}Sr_{2}CaCu_{2}O_{8} has been investigated over long times (up to two weeks) with fast current pulses driven along the ab plane. It is found that at low temperature and high magnetic field both zero field cooled (ZFC) and field cooled (FC) samples relax towards the same equilibrium state, which is much closer to the original ZFC state than to the FC state. The implication of this FC metastability for the vortex phase diagram is discussed in the context of previous measurements., latex ageg.tex, 5 files, 4 figures, 5 pages [SPEC-S01/041], submitted to Phys. Rev. Lett. Text changes

Published
2001

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