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Exchange Magnetostriction in Disordered 2D Ising Ferromagnets

100%
Kawecka-Magiera B., Maksymowicz A., Kułakowski K., Lenda A.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
297-301
EN
We investigate volume and shape magnetoelastic strains of a 2D anisotropic Ising alloy with partial atomic order. Three possible origins of shape strain are distinguished: (i) anisotropy of elastic constants, (ii) anisotropy of magnetic bonds and (iii) anisotropy of the spatial derivatives of magnetic bonds. None of these mechanisms vanishes above the Curie temperature. Equilibrium strains are expressed in terms of anisotropic spin-spin nearest-neighbours correlation functions. These functions are calculated against temperature, both in ferromagnetic and paramagnetic phase. Shape strain decreases monotonously with temperature for the mechanisms (i) and (iii), and has a maximum near the Curie temperature for the case (ii). The results may be relevant for multilayer magnetic systems.
2
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Thin Films Investigations by Means of Spin-Wave Resonance

100%
Maksymowicz A., Maksymowicz L., Whiting J.
Acta Physica Polonica A
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1991
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vol. 80
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issue 5
665-673
EN
Magnetic resonance technique may successfully be applied to determine some basic parameters such as g-factor, magnetization M_{s} or anisotropy energy constant K_{u} in thin magnetic films. These parameters are obtained from a ferromagnetic resonance experiment when uniform precession of M_{s} takes place. From spin-wave resonance one may extract very valuable information on the exchange constant A or the surface conditions characterized by the surface anisotropy energy (or pinning parameters ρ). In fact, it is only spin-wave resonance or similar techniques which allow for measurements of A, ρ or the coupling constant K_{c} between ferromagnetic sublayers in multi-layered structure. The magnetic phase diagram, temperature dependence of the spin-waves stiffness constant, and the anisotropy energy constant may also be listed as less common examples of spin-wave resonance technique application for the investigation of thin films. This paper presents a theoretical approach to typical examples of experimental results and their interpretation from spin-wave resonance measurements.
3
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Magnetic Anisotropy and Magnetostriction of Atom Pairs

100%
Kułakowski K., Maksymowicz A., Magdoń M.
Acta Physica Polonica A
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1994
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vol. 85
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issue 5
869-873
EN
We calculated one-electron hopping contribution to two-ion magnetic anisotropy and shape magnetostriction in amorphous 3d-alloys. Calculations were performed in the narrow band limit and include spin-orbit coupling, the Zeeman orbital and spin magnetic moments terms with possible partial effective quenching of the orbital magnetic moments in metals. The parameters for numerical calculations are expected to correspond to pairs of Fe atoms with the spin-orbit coupling A= 0.03 eV and hopping integrals of about 3 eV. The magnetic anisotropy K changes its sign at some value Δ_{K} of effective magnetic splitting Δ proportional to the magnetization. Then the local easy axis which is parallel to the direction of the pair for small Δ switches to perpendicular easy plane case. K is nearly linear vs. Δ for small Δ and varies roughly as Δ^{3} for large splitting. The dependence of magnetostriction B on Δ is similar to that of magnetic anisotropy K(Δ). For small values of Δ the coefficient B is also linear. Magnetostriction changes its sign at Δ_{B} and becomes positive for Δ greater than Δ_{K}.
4
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Phase Space Description of Localization in Disordered One-Dimensional Systems

100%
Wołoszyn M., Spisak B., Maksymowicz A.
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EN
The degree of electronic localization in disordered one-dimensional systems is discussed. The model is simplified to a set of Diracδ-like functions used for the potential in the Schrödinger equation and calculations are carried out for the ground state. The disorder of topological character is introduced by the random shifts of the potential peaks. For comparison, we also discuss two aperiodic systems of the potential peaks: Thue-Morse and Fibonacci sequences. The localization, both in the momentum and the real space, is analyzed for different disorder strengths and sizes of the system. We calculate the localization length, and additionally we express the localization effects in terms of the inverse participation function and also by means of the Husimi quasi-classical distribution function in the phase space of the electron (position, momentum) coordinate system. We present the influence of disorder generated by the random and aperiodic sequences of potential on the energy spectrum.
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