Temperature dependence of the coercive field in single-domain particle systems

Abstract

The magnetic properties of Cu97Co3 and Cu90Co10 granular alloys were measured over a wide temperature range (2 to 300 K). The measurements show an unusual temperature dependence of the coercive field. A generalized model is proposed and explains well the experimental behavior over a wide temperature range. The coexistence of blocked and unblocked particles for a given temperature rises difficulties that are solved here by introducing a temperature dependent blocking temperature. An empirical factor gamma (γ) arise from the model and is directly related to the particle interactions. The proposed generalized model describes well the experimental results and can be applied to other single-domain particle system.

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

“…The associated NP moment distribution gives rise to a blocking temperature distribution. This behavior was well described by Nunes et al (2004). Above 200 K, H c does not experience any important changes, which may indicate the presence of a small fraction of unusually large particles or the existence of a segregated and magnetically ordered macrophase.…”

“…In such a case, its magnetic moment may fluctuate during the measurement process. Fluctuations can be divided into collective magnetic excitations (small amplitude fluctuation around an easy direction) and superparamagnetic relaxations (magnetization direction fluctuation among the easy directions) (Morup and Topsoe 1976;Morup et al 1980). In a particle with uniaxial anisotropy, the simplest form of its total magnetic anisotropy energy is given by:…”

Current-induced magnetization switching in Pt/Co/Ta with interfacial decoration by insertion of Cr to enhance perpendicular magnetic anisotropy and spin–orbit torques

“…Additionally, as can be seen from Fig. 2(d), H sw displays a linear dependence on the square root of T. The strong temperature dependence in H sw is an indication of the mechanism of thermally activated domain wall (DW) motion, it can be expressed as [25,26] …”

Magnetism in Granular Systems

“…We use the total energy to calculate the magnetization, heat capacity, magnetic susceptibility, and blocking temperature in nanoparticulated systems. The application of our theory to experimental data on nanoparticulated systems [3][4][5] and for the Fe-Al, Fe-Si, and Fe-Mn-Al microparticulated granular systems [6][7][8] will be presented elsewhere.…”