Magnetization reversal mechanisms and time-dependent processes in Tb - Fe - Co alloy films

Abstract

In this paper we develop an interpretation of magnetization data appropriate to materials where magnetization reversal occurs as a two-stage process: domain nucleation followed by domain wall motion, and apply it to films with perpendicular magnetic anisotropy. An interpretation of remanence curve data and time dependence data for a two-stage reversal system is proposed. The two principal remanence curves (IRM and DCD) yield data on the energy barrier distribution, while the delta-I plot which compares these two remanence curves offers a method of characterizing the relative importance of domain nucleation and domain wall motion. The interpretation is then applied to a series of magneto-optic thin films where the film thickness varies from 164 to 830 Å. All but the thickest film show magnetization reversal is controlled by both domain nucleation and domain wall motion. In the 830 Å film only domain wall motion appears important in controlling reversal.

Magnetization reversal process in a nanoscale Fe/FeOxide granular system

“…According to the XRD analysis, D ¼ ð671Þ nm and the Fe volume fraction is B20%: The general magnetic behavior of the sample is the expected one, in agreement with [1]. The isothermal remanence (IRM) and the demagnetized remanence (DCD) was measured, on the compacted nanoparticles, according to a standard procedure [2], at 5 KpTp250 K by a commercial SQUID magnetometer.…”

“…At T ¼ 300 K; the net moments of the oxide regions are free to thermally fluctuate, but the passage to a pure (super)-paramagnetic state is prevented by the polarizing action of the Fe particle moments. With decreasing T; a progressive freezing of the oxide moments occurs, according to the distribution of effective anisotropy energy barriers centered at TB150 K: Below such temperature, an exchange bias effect originates from the coupling between the Fe and the oxide magnetic phases, becoming stronger with decreasing T: Below TB20 K; the freezing of the oxide in a cluster-glass-like state is complete and the interplay between oxide-particle and particle-particle interactions results in a frozen state for the whole system [1].In this work, the Fe/FeOxide system has been investigated by the remanence curve technique, usually employed to study the effect of magnetic interactions on the magnetization process in particulate magnetorecording materials, through the DI plots [2]. The aim of the investigation was to establish how the method unfolds the actual magnetic behavior of such complex system, fully determined by the anisotropy energy barrier distribution of the oxide phase, by the oxideparticle exchange coupling and by the particle-particle dipolar interactions.…”

“…In this work, the Fe/FeOxide system has been investigated by the remanence curve technique, usually employed to study the effect of magnetic interactions on the magnetization process in particulate magnetorecording materials, through the DI plots [2]. The aim of the investigation was to establish how the method unfolds the actual magnetic behavior of such complex system, fully determined by the anisotropy energy barrier distribution of the oxide phase, by the oxideparticle exchange coupling and by the particle-particle dipolar interactions.…”

Current Density and Thickness Effects on Magnetic Properties of Electrodeposited CoPt Magnetic Films

“…Here, M and M o are the net magnetizations of time t and t o , respectively, and S is the magnetic viscosity coefficient which is generally positioned near the coercivity. If the time dependence of the magnetic moment complies with this relationship, the wall pinning is regarded as the main magnetization reversal behavior for the samples [14]. Figure 4 shows the field dependence of the magnetic moment decay curves and magnetic viscosity coefficient for the 15 nm sample.…”

Nucleation of magnetisation reversal, from nanoparticles to bulk materials

“…The hysteresis loop morphology is then completely different [40]. Thomson distributions, and the influence of this distribution on the relative contribution of domain nucleation and domain wall propagation to the magnetisation reversal [51]. Since domain wall propagation initiated at a limited number of nucleation centers is a relatively slow process, a distribution of energy barriers for nucleation in continuous films usually shows up as an increase of the nucleation rate at increasing applied field sweep rate [43,48].…”