Inverted Hysteresis Loops in the Fe73.5Cu1Nb3Si13.5B9 Alloy With Small Coercivity

The phenomenon of inverted hysteresis loop has been observed in many materials for the past decades. However, the physical origin of the inverted hysteresis loop has long been debated. Here, we report the completely inverted hysteresis loop with a clockwise cycle in the soft-magnetic nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy and amorphous Fe73.5Cu1Nb3Si13.5B9 alloy at room temperature. The negative remanence and positive coercivity were observed in the descending branch of magnetization curve when the scan field range was above 1 KOe. By comparing the results with that of the standard Pd sample, we found that the net coercivities of the nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy and standard Pd sample are almost equal for the different scanning field ranges. Therefore, it is confirmed that the phenomenon of completely inverted hysteresis loop is caused by the remanence of superconducting magnet rather than the structural inhomogeneity effects. Our results suggest that special care should be taken during the measurement of hysteresis loops using MPMS 3, especially for the materials with small coercivity.

Mittag–Leffler Function as an Approximant to the Concentrated Ferrofluid’s Magnetization Curve

In this work, we show that the static magnetization curve of high-concentrated ferrofluids can be accurately approximated by the Mittag–Leffler function of the inverse external magnetic field. The dependence of the Mittag–Leffler function’s fractional index on physical characteristics of samples is analysed and its growth with the growing degree of system’s dilution is revealed. These results provide a certain background for revealing mechanisms of hindered fluctuations in concentrated solutions of strongly interacting of the magnetic nanoparticles as well as a simple tool for an explicit specification of macroscopic force fields in ferrofluid-based technical systems.

Magnetic Characterization by Scanning Microscopy of Functionalized Iron Oxide Nanoparticles

This study aimed to systematically understand the magnetic properties of magnetite (Fe3O4) nanoparticles functionalized with different Pluronic F-127 surfactant concentrations (Fe3O4@Pluronic F-127) obtained by using an improved magnetic characterization method based on three-dimensional magnetic maps generated by scanning magnetic microscopy. Additionally, these Fe3O4 and Fe3O4@Pluronic F-127 nanoparticles, as promising systems for biomedical applications, were prepared by a wet chemical reaction. The magnetization curve was obtained through these three-dimensional maps, confirming that both Fe3O4 and Fe3O4@Pluronic F-127 nanoparticles have a superparamagnetic behavior. The as-prepared samples, stored at approximately 20 °C, showed no change in the magnetization curve even months after their generation, resulting in no nanoparticles free from oxidation, as Raman measurements have confirmed. Furthermore, by applying this magnetic technique, it was possible to estimate that the nanoparticles’ magnetic core diameter was about 5 nm. Our results were confirmed by comparison with other techniques, namely as transmission electron microscopy imaging and diffraction together with Raman spectroscopy. Finally, these results, in addition to validating scanning magnetic microscopy, also highlight its potential for a detailed magnetic characterization of nanoparticles.

Calculation of the current converters magnetic circuits taking into account the dependence nonlinearity of the specific magnetic resistance relative the magnetic induction

The magnetic circuits of a current converter, the work principle of which is based on the nonlinearity of the magnetization curve, are considered. In order to improve the analytical calculation accuracy of magnetic circuits, it is necessary to establish a relationship between the specific magnetic resistance and magnetic induction. Methods for solving differential equations for magnetic circuits of a converter with longitudinally distributed parameters and an expression for the dependence of the specific magnetic resistance relative the magnetic induction are presented. Keywords electromagnetic current converter; magnetic circuit; nonlinearity of the magnetization curve; magnetic flux; magnetomotive force; quasi-linearization method; machine method of calculation

Hysteresis branch crossing and the Stoner–Wohlfarth model

The Stoner–Wohlfarth model predicts the crossing of the ascending and descending branches of the hysteretic magnetization curve. This crossing behavior has widely been dismissed, with the claim that it violates the laws of thermodynamics. Experimental verification of hysteresis branch crossing has not been acknowledged in the literature. Here we show, both theoretically and experimentally, that the crossing of the ascending and descending branches of the magnetization curve is a robust, reproducible phenomenon which does not violate any fundamental law.