Superparamagnetism and Monte Carlo Simulations

Abstract

Abstract:We summarize the basic concepts beneath the idea of superparamagnetism and introduce the Monte Carlo (MC) method as a powerful tool for studying superparamagnetic (SPM) properties. Starting with the description of the physical features of the single-domain SPM entities, we concentrate on their special magnetic properties as a function of time, temperature, and applied magnetic field. Then, we give a general approach to the use of a MC technique for studying SPM properties, focusing on the use of the Metropolis algorithm and discussing the importance of the choice of the MC steps in the simulations.

Synthesis, Characterization, and Evaluation of Superparamagnetic Doped Ferrites as Potential Therapeutic Nanotools

“…In particular, MNPs based on iron oxides are particularly suitable for several of the previously mentioned applications as a consequence of their low toxicity and high magnetic power, among other characteristics. The properties of MNPs depend strongly on their physicochemical characteristics, but the size is one of the most influential factors that define their behavior, with some critical dimensions existing below which these types of nanostructured systems enter the so-called superparamagnetic regime. , In this regime, the behavior of the magnetization of MNPs when the applied magnetic field is modified involves a hysteresis loop with a negligible area, which for practical purposes is translated into a very low tendency to form particle clusters/aggregates under the application of an external magnetic field, which is of great importance in many of their potential in vivo bioapplications . For these reasons, current research in this field is focusing on the design and obtaining of MNPs with a high magnetic power without significant increases in particle dimensions.…”

Magnetic Nanocomposite Hydrogels for Tissue Engineering: Design Concepts and Remote Actuation Strategies to Control Cell Fate

“…53 Among the different MNPs characteristics, the size is one of the most influential factors that define the behavior of MNPs composed of ferro-/ferrimagnetic materials, existing some critical dimensions below which these types of nanoparticles enter the so-called superparamagnetic regime. 54 In this regime, the thermal energy of MNPs can exceed their magnetic stabilization energy, resulting in a demagnetization of the particles when the applied magnetic field is removed; that is, the magnetic hysteresis loops of the magnetization vs applied magnetic field plots show negligible areas (M R and H C equal to zero) (Figure 3a). 55 For practical purposes, the absence of permanent magnetic moment is translated into a high remote control over the MNPs distribution and a very low tendency to form particle clusters/aggregates under the application of an external magnetic field, which is of great importance in many of their potential bio-applications.…”

“…Among the different MNPs characteristics, the size is one of the most influential factors that define the behavior of MNPs composed of ferro-/ferrimagnetic materials, existing some critical dimensions below which these types of nanoparticles enter the so-called superparamagnetic regime . In this regime, the thermal energy of MNPs can exceed their magnetic stabilization energy, resulting in a demagnetization of the particles when the applied magnetic field is removed; that is, the magnetic hysteresis loops of the magnetization vs applied magnetic field plots show negligible areas ( M R and H C equal to zero) (Figure a) .…”

Effect of particle size distribution on magnetic behavior of nanoparticles with uniaxial anisotropy

“…where k B is the Boltzmann constant, K 1 V is the energy barrier height in the absence of applied field, and τ o is the characteristic relaxation time (∼ 10 −9 s). [22,23] Here, T over T B defines the state of the system. For T < T B , the particles are in a blocked state and possess pure ferromagnetic features, which can be simulated by the two-state model.…”