In this paper we utilize the Landau-Lifshitz equation and its properties to derive a scalar equation of motion and analyze a chain of spins and model clusters of spins in materials that in principle not are ferromagnetic, such as aluminum and others. By calculating the total energy of the system of all interactions between the spins, the Landau-Lifshitz equation governs the local behavior of spins or a chain of spins. This model is well known and so called Heisenberg model. We used the Heisenberg model to write the Hamiltonian of the system and got there the equation of that govern the spin chain dynamics. However, in some systems the approximation of a single magnetic phase may not reflect observations. For example, the observation of superparamagnetism and spontaneous magnetization reversal can be better explained through the interaction between magnetic phases. Such behavior has been observed in both nanoparticles and thin films, and can result in novel behavior such as inverted hysteresis loops. A revised Heisenberg model is proposed to describe this behavior. We also discuss the description of the pattern of the magnetization scalar field through the use of the Schrödinger-like equation, which may contribute to modeling the behavior of the magnetization field at the interface of hybrid materials.
Magnetic thin films are proposed for a range of spintronic and other applications. While exploring so-called magnetic “dead layers” in La0.7Sr0.3MnO3 thin films, we detect a magnetic phase competition between two types of magnetic order. This competition leads to spontaneous magnetization reversal, which had not previously been observed in epitaxial thin films. This effect allows switching the magnetization direction with very small applied magnetic fields, which could significantly benefit spintronic and other applications.
La0.7Sr0.3MnO3 is a strongly correlated complex oxide. There is limited information about La0.7Sr0.3MnO3 thin films’ transient reflectivity (TR), where differences in ultra-fast dynamics due to surface and interface effects are expected. By decreasing the film thickness, additional energy states emerge, providing extra relaxation channels. Due to the reduced absorption in thin films, observing the effects of these extra states in TR signal is challenging, especially in a hole doped system such as La0.7Sr0.3MnO3. Moreover, in lower thicknesses, sinusoidal behavior superimposed on the TR signal is not analyzable by Fourier transforms. Wavelet transforms are perfect tools to analyze these fast-vanishing oscillations.
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