Papers by Andrzej Majhofer
Testing the interpretation of the γ-γ correlation experiments at high spins
Nuclear Instruments and Methods in Physics Research, 1982
Abstract Recently developed methods of dealing with experimental γ-γ correlation data are examine... more Abstract Recently developed methods of dealing with experimental γ-γ correlation data are examined using the numerical simulation of the experiment.
Magnetic Properties of Chains of Spherical Nanoparticles with Cubic Magnetic Anisotropy: A Monte Carlo Study
1. Introduction Molecular beam epitaxy has become an important tool to prepare ultrathin films an... more 1. Introduction Molecular beam epitaxy has become an important tool to prepare ultrathin films and nanostructures in nonequilibrium states that show novel properties distinctly different from the equilibrium bulk phases. Theoretically, the question arises how to relate the structural characteristics of the growing material to the incoming flux and temperature-dependent surface diffusion constants. This question is fairly well understood for one-component systems. By contrast, only few theoretical studies were devoted to the growth of binary alloy nanostructures, despite of the large interest in this field from the experimental and technological viewpoint. In this communication we present detailed kinetic Monte Carlo simulations of growing nanoclusters within a binary alloy model that allows arbitrary diffusion moves of atoms within an active zone near the cluster surface. Our model is designed to describe fcc-type alloys under growth in the (111) direction. The main motivation came ...
Crystals, 2018
Zinc oxide nanoparticles codoped with Co2+ and Mn2+ ions (Zn(1−x−y)MnxCoyO NPs) were obtained for... more Zinc oxide nanoparticles codoped with Co2+ and Mn2+ ions (Zn(1−x−y)MnxCoyO NPs) were obtained for the first time by microwave solvothermal synthesis. The nominal content of Co2+ and Mn2+ in Zn(1−x−y)MnxCoyO NPs was x = y = 0, 1, 5, 10 and 15 mol % (the amount of both ions was equal). The precursors were obtained by dissolving zinc acetate dihydrate, manganese (II) acetate tetrahydrate and cobalt (II) acetate tetrahydrate in ethylene glycol. The morphology, phase purity, lattice parameters, dopants content, skeleton density, specific surface area, average particle size, average crystallite size, crystallite size distribution and magnetic properties of NPs were determined. The real content of dopants was up to 25.0% for Mn2+ and 80.5% for Co2+ of the nominal content. The colour of the samples changed from white to dark olive green in line with the increasing doping level. Uniform spherical NPs with wurtzite structure were obtained. The average size of NPs decreased from 29 nm to 21 nm...
Carbon-Encapsulated Magnetic Nanoparticles Based on Fe, Mn, and Cr for Spintronics Applications
Acta Physica Polonica A, 2007
Adjustment of the pairing force strength to the experimental data and the optimised Woods-Saxon potential spectrum-comparison with the Nilsson model
Journal of Physics G: Nuclear Physics, 1980
... 447 Page 3. 448 J Dudek, A Majhofer and J Skalski G, and G, , for protons and neutrons, respe... more ... 447 Page 3. 448 J Dudek, A Majhofer and J Skalski G, and G, , for protons and neutrons, respectively, after parametrising them in the form of simple functions of the proton and neutron numbers. ... G = Go/A + GI(N - Z)/A. Page 5. 450 J Dudek, A Majhofer and J Skalski ...
Thermally activated flux motion in a one-dimensional Josephson-junction array with self-inductances
Physical Review B, 1996
We study relaxation of magnetic flux in a one-dimensional network of resistively shunted Josephso... more We study relaxation of magnetic flux in a one-dimensional network of resistively shunted Josephson junctions. Magnetic fields due to the currents induced in the system are taken into account via self-inductance coefficients. A master equation is derived that describes the stochastic motion of flux quanta among the different plaquettes of the network. Space- and time-dependent flux profiles are calculated within mean-field theory and also by a continuous-time Monte Carlo algorithm. The relevance of our results for the description of flux creep experiments in strongly inhomogeneous superconductors is pointed out.
Physical Review B, 2003
Using an atom-vacancy exchange algorithm, we investigate the kinetics of the order-disorder trans... more Using an atom-vacancy exchange algorithm, we investigate the kinetics of the order-disorder transition in an fcc A3B binary alloy model following a temperature quench from the disordered phase. We observe two clearly distinct ordering scenarios depending on whether the final temperature T f falls above or below the ordering spinodal Tsp, which is deduced from simulations at equilibrium. For shallow quenches (T f > Tsp) we identify an incubation time Ï„inc which characterizes the onset of ordering through the formation of overcritical ordered nuclei. The algorithm we use together with experimental information on tracer diffusion in Cu3Au alloys allows us to estimate the physical time scale connected with Ï„inc in that material. Deep quenches, T f < Tsp, result in spinodal ordering. Coarsening processes at long times proceed substantially slower than predicted by the Lifshitz-Allen-Cahn t 1/2 law. Structure factors related to the geometry of the two types of domain walls that appear in our model are found to be consistent with Porod's law in one and two dimensions.
Physical Review B, 1991
We investigate the magnetic behavior of a two-dimensional network of resistively-shunted (zerocap... more We investigate the magnetic behavior of a two-dimensional network of resistively-shunted (zerocapacitance) Josephson junctions, treating magnetic screening effects in a self-consistent manner. By this, we obtain stationary distributions of magnetic Aux and hysteresis effects typical of single crystals or ceramic samples of high-T, superconductors, depending upon the magnitude of the magnetic penetra- tion depth XJ.
Physical Review B, 2001
Within the atom-vacancy exchange mechanism in a nearest-neighbor interaction model we investigate... more Within the atom-vacancy exchange mechanism in a nearest-neighbor interaction model we investigate the kinetics of surface-induced ordering processes close to the (001) surface of an fcc A3Balloy. After a sudden quench into the ordered phase with a final temperature above the ordering spinodal, T f > Tsp, the early time kinetics is dominated by a segregation front which propagates into the bulk with nearly constant velocity. Below the spinodal, T f < Tsp, motion of the segregation wave reflects a coarsening process which appears to be slower than predicted by the Lifschitz-Allen-Cahn law. In addition, in the front-penetrated region lateral growth differs distinctly from perpendicular growth, as a result of the special structure of antiphase boundaries near the surface. Our results are compared with recent experiments on the subsurface ordering kinetics at Cu3Au (001).
Physical Review E, 1993
We formulate a method designed for lattice-gas problems that is analogous to the density-function... more We formulate a method designed for lattice-gas problems that is analogous to the density-functional theory used to describe equilibrium properties of inhomogeneous classical liquids. After a discussion of the difI'erences between the discrete and the continuous forms of the theory we present a quantitative test for a one-dimensional system. Possible applications of our approach to order-disorder transitions in lat- tice gases are pointed out. PACS number(s): 05.50.+ q Lattice gases, i.e. , ensembles of interacting particles distributed on discrete lattices, are used as one of the most universal tools in modeling static and dynamic properties of different physical systems. With various in- teractions, lattice geometries and boundary conditions, such models were successfully used to describe order- disorder transitions in alloys [1 -3], general characteris- tics of phase transitions [4,5], diffusion processes in solids
Physical Review E, 1993
An alternative approach to ordering transitions in lattice gases is presented. Our approach can b... more An alternative approach to ordering transitions in lattice gases is presented. Our approach can be re- garded as the lattice analog of the well-known freezing theory for continuous fluids based on density functionals. Specifically, we discuss ordering in a three-dimensional model involving repulsive forces up to second neighbors and compare our results with Monte Carlo simulations. The utility of our method is demonstrated further by calculating the structure of a planar interface between coexisting ordered and disordered phases. It is pointed out that our theory is a good starting point for investigating problems of the interfacial kinetics.
Testing the interpretation of the ?-? correlation experiments at high spins?
Nuclear Instruments and Methods in Physics Research, 1982
Metastable effects and random polarities of magnetic moments in disordered systems of Josephson junctions
Physical Review B, 1990
We use the Monte Carlo technique to simulate experiments on zero-field-cooled (ZFC) and field-coo... more We use the Monte Carlo technique to simulate experiments on zero-field-cooled (ZFC) and field-cooled (FC) superconducting samples. As our model we take a three-dimensional, strongly disordered system of Josephson junctions. For fields exceeding a certain critical value Hc1, we find well-pronounced differences between ZFC and FC magnetizations. At low temperatures, the diamagnetic response of FC samples cooled at Hc1 is
Spectral dimensionality and hyperscaling
Physical Review B, 1986
ABSTRACT
Monte Carlo simulations of a disordered, three-dimensional system of Josephson junctions
Physical Review B, 1989
Using a Monte Carlo technique we study properties of a disordered three-dimensional system of Jos... more Using a Monte Carlo technique we study properties of a disordered three-dimensional system of Josephson junctions. We focus on the anisotropy of the critical magnetic field and on relaxation processes in a zero-field-cooled sample.
Physical Review B, 1994
We compute current-voltage characteristics of an array of resistively shunted Josephson junctions... more We compute current-voltage characteristics of an array of resistively shunted Josephson junctions with screening e6ects treated self-consistently by introducing inductance coefficients. The flux distribu- tion and flux motion through the system is analyzed in the presence of transport currents and of an external magnetic field. We also discuss the applicability of our model to describe inhomogeneous high- T, superconductors.
Physics Letters B, 1982
Shell effects accompanying fast rotation are examined using the cranked Nilsson and Woods-Saxon a... more Shell effects accompanying fast rotation are examined using the cranked Nilsson and Woods-Saxon average nuclear potentials. The single particle states in strongly elongated nuclei (with a quadrupole deformation ~2 ~ 0.65 equivalent to the axis ratio 2 : 1) are analysed. From the relatively large gaps in the single-particle spectra of rotating nuclei the proton and neutron magic numbers are deduced (Z = 64, 66, 75,76; N = 82, 88) which correspond to shell closures at large deformations and high spins. The nuclear spin values associated with the superdeformed states estimated from the Woods-Saxon spectra are roughly 30 to 40 percent lower than the ones obtained within the Nflsson model. This discrepancy is attributed to the presence of the/2 term in the Nilsson potential.
Magnetic interactions in an ensemble of cubic nanoparticles: A Monte Carlo study
Physical Review B, 2013
Ferromagnetic properties ofp-(Cd,Mn)Te quantum wells: Interpretation of magneto-optical measurements by Monte Carlo simulations
Physical Review B, 2009
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Papers by Andrzej Majhofer