Metrological aspects of an automated method for measuring electrophysical parameters of soft magnetic materials

The structure of an automated system for measuring magnetic-hysteresis loops, normal magnetization curve, magnetic permeability with an error of no more than ± 1% is proposed. The measuring principle is based on the inferential measurements of the magnetic induction and the coercive force by integrating the secondary voltage and the excitation current. As a result of metrological analysis, an increase in the measurements accuracy is achieved both by improving the hardware implementation and calibrating the measuring channels, by introducing a correction for the systematic component of the error.

Magnetic Properties and Local Structure of the (La, Co) Co-Doped Bi1−xLaxFe0.95Co0.05O3

In this study, the structural, morphological, and magnetic properties and the local structure of Bi1−xLaxFe0.95Co0.05O3 (x = 0.05, 0.10, 0.15, 0.20) nanoparticles were systematically investigated. In the (La, Co) co-doped BiFeO3 samples, a structural transition from a rhombohedral to orthorhombic structure was observed via X-ray diffraction. This structural phase transition resulted in significantly improved magnetic properties (Ms = 1.706 emu/g at 60 kOe). SEM analysis revealed that grain size decreased with increasing La concentration. The magnetic hysteresis loops confirmed that the significant enhancement of magnetization for all samples. Finally, combining the experimental synchrotron radiation techniques, we studied the samples’ local structure in order to analyze the reasons why the samples’ magnetic properties were enhanced.

Reconstructing phase-resolved hysteresis loops from first-order reversal curves

The first order reversal curve (FORC) method is a magnetometry based technique used to capture nanoscale magnetic phase separation and interactions with macroscopic measurements using minor hysteresis loop analysis. This makes the FORC technique a powerful tool in the analysis of complex systems which cannot be effectively probed using localized techniques. However, recovering quantitative details about the identified phases which can be compared to traditionally measured metrics remains an enigmatic challenge. We demonstrate a technique to reconstruct phase-resolved magnetic hysteresis loops by selectively integrating the measured FORC distribution. From these minor loops, the traditional metrics—including the coercivity and saturation field, and the remanent and saturation magnetization—can be determined. In order to perform this analysis, special consideration must be paid to the accurate quantitative management of the so-called reversible features. This technique is demonstrated on three representative materials systems, high anisotropy FeCuPt thin-films, Fe nanodots, and SmCo/Fe exchange spring magnet films, and shows excellent agreement with the direct measured major loop, as well as the phase separated loops.

Магнитные и радиопоглощающие свойства поликристаллического феррита-шпинели Li-=SUB=-0.33-=/SUB=-Fe-=SUB=-2.29-=/SUB=-Zn-=SUB=-0.21-=/SUB=-Mn-=SUB=-0.17-=/SUB=-0-=SUB=-4-=/SUB=-

Polycrystalline spinel ferrites of the composition Li0.33Fe2.29Zn0.21Mn0.17O4 were synthesized by using the ceramic technology method at sintering temperatures of 950 ° C, 1000 ° C, 1050 ° C, and 1100 ° C. Magnetic hysteresis loops and magnetic permeability of the experimental samples were studied in the range of magnetic fields of -400–400 A/m. In the frequency range of 0.01–7.0 GHz, the behavior of the complex dielectric and complex magnetic permeability, as well as the reflection coefficient on a metal plate, are investigated. It was found that the optimal sintering temperature range for synthesized ferrites is from 1050 ° C to 1100 ° C. It is shown that the spinel ferrite Li0.33Fe2.29Zn0.21Mn0.17O4 intensely absorbs electromagnetic radiation in the frequency range from 0.05 to 7.0 GHz. Possibilities of practical application of the obtained results are discussed.

A laboratory magnetometer for express measurements of magnetic hysteresis loops

Subject and Purpose. The development of technologies for synthesis of nanoscale magnetic materials requires new techniques for measuring magnetic properties of nanoscale magnetic materials in such a way as to provide express post-synthesis measurements of magnetic properties and exclude, in doing so, any mechanical displacements of measured specimens. Despite the fact that numerous techniques exist for studying magnetic properties of materials, the development of such magnetic nanomaterials as magnetic nanoparticles faces the need in novel measuring approaches based on standard procedures. Novel express techniques are called to gain information about how magnetic properties of magnetic materials vary over time and respond to such factors as temperature, storage conditions, stabilizing agents, exposure to an external magnetic field. Method and Methodology. In this work, magnetic hysteresis loops are registered using a newly developed technique based on the method of small disturbances (by an external magnetic field) and combining standard constructions of hysterometers and vibrating-sample magnetometers. Results. Magnetic hysteresis loops of a bulky ferrite (brand 1SCh4) sample and a 40 μm thick YIG film have been registered using the presented technique and compared with the results obtained by the well-known technique for measuring magnetic hysteresis loops. They are in good agreement with a margin error as low as 10%, which can be further improved by means of more precise equipment. With the presented technique, the magnetization and the coercive force of Fe0.5Co0.5Fe2O4 nanoparticles not examined yet have been determined. Conclusion. The developed technique makes it possible to study magnetic materials of various compositions including nanoscale magnets.

Asymmetric Hysteresis Loops in Co Thin Films

Asymmetric magnetic hysteresis loops are usually found in exchange bias (EB) systems, typically after field cooling a system below the Néel temperature of an antiferromagnet exchange coupled to a ferromagnet. Alternatively, asymmetric hysteresis loops may occur due to undetected minor loops or in systems with a rotational anisotropy. Here, we report on an exchange bias thin film system MgO(100)/Co/CoO, examined at room temperature, which is far above the blocking temperature, by the magneto-optical Kerr effect (MOKE). While the longitudinal hysteresis loops partly show steps which are well-known from diverse purely ferromagnetic systems, the transverse hysteresis loops exhibit clear asymmetries, similar to exchange biased systems at low temperatures, and unusual transverse magnetization values at saturation. Since minor loops and a rotational anisotropy can be excluded in this case, this asymmetry can possibly be a residue of the exchange bias coupling at lower temperatures.

A Study of Temperature-Dependent Hysteresis Curves for a Magnetocaloric Composite Based on La(Fe, Mn, Si)13-H Type Alloys

In the present paper, the effect of temperature on the shape of magnetic hysteresis loops for a magnetocaloric composite core was studied. The composite core, based on La(Fe, Mn, Si)13-H, was set up using three component disks with different Curie temperatures. The magnetic properties of the components and the outcome composite core were determined using a self-developed measurement setup. For the description of hysteresis loops, the phenomenological T(x) model was used. The presented methodology might be useful for the designers of magnetic active regenerators.