Residual Magnetic Moment Influences the Features of Fe3s XPS Spectrum: A Case Study

Background: Fe 3sXPS spectrumexhibits doublet peak instead of predicted singlet peak based on spin-orbit coupling theory. This anomalous behavior is considered to be magnetic origin. However, the effect of residual magnetic moment to the features of Fe3s doublet peakis not understood fully. Objective: This study aims to verify the effect of residual magnetic moment on the spectral features of Fe3s XPS spectrum of magnetic material. Method: As a case study, we have carried out a high temperature XPS study of the Fe 3s spectrum of magnetic domain aligned (MDA) sample with composition composed of SrFe10.8Al1.2O19. In addition, the XPS data have been compared with the data acquired at different temperatures of magnetic domain non-aligned (MDNA) sample. Results: The results show that the majority peak intensity and minority peak width of Fe 3s spectrum of MDA are smaller than those of the MDNA sample, and they increase systematically with increasing temperature. However, it is noted that the features of Fe3s spectrum of both MDA and MDNA samples are completely overlapped near and above the Curie temperature, Tc ~ 670K. Conclusion: The analysis of XPS data suggests that the residual magnetic moment influences the spectral features of Fe3s spectrum. These results provide evidences that it is important to consider the contribution of residual magnetic moment while deriving information from Fe 3s XPS spectrum of MDA sample.

High Absorption Electromagnetic Wave Properties of Composite CoFeO3 Synthesized by Simple Mechanical Alloying

Electronic equipment demand is strongly correlated to the electromagnetic wave interference (EMI), which causes severe effects on human health. Microwave absorbing materials (MAMs) are one method to protect human health from EMI. Cobalt nanoparticles show high performance as MAMs. Here, we have synthesized CoFeO3 by simple mechanical alloying for increased multiple reflections, interfacial polarization, magnetic domain loss, electron spin loss, internal resonance, hoping electron, conductive loss, and multiple scattering for improved absorption of EMI waves. We determined the electronic properties from the Quantum Espresso (QE) and corresponding results are discussed. The metallic character comes from the d-state of transition metal atoms Fe (II) and Co which are sufficiently large in magnitude in the Fermi level of band structure and density of state (DOS) distribution. Crystallite size in the range of 13.6 to 18.7 nm with surface morphology shows irregular shapes of the particles. For CoFeO3 as MAMs, we found that the reflection loss (RL) is -55 dB (lower than the previous reported -43.2 dB) at 10-11 GHz for a thickness of 8 mm, indicating that this study shows high potential of CoFeO3 as an alternative composite for MAMs applications.

Sputter Deposited Magnetostrictive Layers for SAW Magnetic Field Sensors

For the best possible limit of detection of any thin film-based magnetic field sensor, the functional magnetic film properties are an essential parameter. For sensors based on magnetostrictive layers, the chemical composition, morphology and intrinsic stresses of the layer have to be controlled during film deposition to further control magnetic influences such as crystallographic effects, pinning effects and stress anisotropies. For the application in magnetic surface acoustic wave sensors, the magnetostrictive layers are deposited on rotated piezoelectric single crystal substrates. The thermomechanical properties of quartz can lead to undesirable layer stresses and associated magnetic anisotropies if the temperature increases during deposition. With this in mind, we compare amorphous, magnetostrictive FeCoSiB films prepared by RF and DC magnetron sputter deposition. The chemical, structural and magnetic properties determined by elastic recoil detection, X-ray diffraction, and magneto-optical magnetometry and magnetic domain analysis are correlated with the resulting surface acoustic wave sensor properties such as phase noise level and limit of detection. To confirm the material properties, SAW sensors with magnetostrictive layers deposited with RF and DC deposition have been prepared and characterized, showing comparable detection limits below 200 pT/Hz1/2 at 10 Hz. The main benefit of the DC deposition is achieving higher deposition rates while maintaining similar low substrate temperatures.

Enhanced Reversible Magnetic-Field-Induced Strain in Ni-Mn-Ga Alloy

A phase-field model was developed to simulate the ferromagnetic domain structure and martensite variant microstructure of Ni-Mn-Ga shape-memory alloy. The evolution of reversible magnetic-field-induced strain (MFIS) and associated magnetic domain/martensite variant structure were modeled under an external magnetic field. It was found that MFIS increased significantly from 0.2% to 0.28% as the temperature increased from 265 K to 285 K. In addition, compressive pre-stress efficiently enhanced the MFIS of the alloy, while tensile stress reduced MFIS. Furthermore, it was proved that there was possibility of achieving similar enhancement of MFIS by replacing compressive stress with perpendicular biaxial tensile stress. The results revealed that the residual variant induced by stress plays an important role in the reversible MFIS effect.

A mechanically strong and ductile soft magnet with ultralow coercivity

Soft magnetic materials (SMMs) are indispensable components in electrified applications and sustainable energy supply, allowing permanent magnetic flux variations in response to high frequency changes of the applied magnetic field, at lowest possible energy loss1. The global trend towards electrification of transport, households and manufacturing leads to a massive increase in energy consumption due to hysteresis losses2. Therefore, minimizing coercivity, which scales the losses in SMMs, is crucial3. Yet, meeting this target alone is not enough: SMMs used for instance in vehicles and planes must withstand severe mechanical loads, i.e., the alloys need high strength and ductility4. This is a fundamental design challenge, as most methods that enhance strength introduce stress fields that can pin magnetic domains, thus increasing coercivity and hysteretic losses5. Here, we introduce a new approach to overcome this dilemma. We have designed a Fe-Co-Ni-Ta-Al multicomponent alloy with ferromagnetic matrix and paramagnetic coherent nanoparticles of well-controlled size (~91 nm) and high volume fraction (55%). They impede dislocation motion, enhancing strength and ductility. Yet, their small size, low coherency stress and small magnetostatic energy create an interaction volume below the magnetic domain wall width, leading to minimal domain wall pinning, thus maintaining the material’s soft magnetic properties. The new material exhibits an excellent combination of mechanical and magnetic properties outperforming other multicomponent alloys and conventional SMMs. It has a tensile strength of ~1336 MPa at 54% tensile elongation, an extremely low coercivity of ~78 A/m (<1 Oe) and a saturation magnetization of ~100 Am2/kg. The work opens new perspectives on developing magnetically soft and mechanically strong and ductile materials for the sustainable electrification of industry and society.

Mathematical Study of Imposed Magnetic Field on Radiative Hydromagnetic Casson Fluid Flow in a Micro-Channel with Asymmetric Heating

The work of steady hydromagnetic stream of Casson liquid in a micro-channel constructed by two indefinite vertical proportionate walls in the appearance of thermal radiation is presented in this article. The effect of an imposed magnetic domain appearing scheduled to movement of an electrically administrating liquid is adopted into account. The exact solutions of the liquid velocity, imposed magnetic domain, and temperature domain have been obtained. Also, the analytical expressions for the skin-friction coefficient and imposed current density are obtained. The basic aspiration of this article is to reinvestigate the supremacy of pertinent physical constraints like magnetic Prandtl number, injection/suction parameter, Hartmann number, thermal radiation parameter, rarefaction parameter, wall ambient temperature difference ratio, and liquid wall interaction parameter over the imposed magnetic field and velocity of the liquid. Lorentz force which is obtained from magnetic field has a propensity to decline the motion of liquid and imposed magnetic field. The imposed current density rises with an enhancement in the hydromagnetic Prandtl number. This study is applied in the machines like transformers, generators, and motors work on the principle of electromagnetic induction. Results are compared with the literature in the limiting case.