Magnetic, magnetocaloric properties and phenomenological model in amorphous Fe40Ni38Mo4B18 alloy

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Abstract

We investigate in detail the magnetic, magnetocaloric properties and phenomenological model of amorphous Fe40Ni38Mo4B18 alloy. The melt spinning method has been used to synthesize the amorphous alloy. With a Curie temperature of 610 K, the magnetic transition nature undergoes a second-order magnetic phase transition from ferromagnetic to paramagnetic states. The magnetic entropy change (-ΔSM) is determined using the thermodynamic Maxwell’s relation. Moreover, we report a theoretical investigation of the magnetocaloric effect using a phenomenological model. The best model parameters and their variation with temperature and the magnetic field were obtained. The theoretical predictions were found to be in line with the experimental results.

Introduction

Magnetic amorphous alloys have attracted great attention during several years, for both their fundamental physics of magnetism and technological levels. However, their magnetic properties depend considerably on the fabrication method. The amorphous alloys prepared by melt spinning method can be utilized in electronic transformers and recording heads [1]. Amorphous Fe40Ni38Mo4B18 alloy (commercially named as METGLAS2826MB) undergo interesting changes in magnetic behavior with Mo concentration and temperature. It is one of the good soft magnetic materials [2], [3], [4], because of its moderate saturation magnetization, high permeability, low coercivity, low saturation magnetostriction, and low core loss. Therefore, it is interesting to investigate the magnetocaloric effect MCE [5], [6], [7], [8] in such systems.

There are two important parameters (in addition to the adiabatic temperature change) which characterize the magnetocaloric effect: the magnetic entropy change ΔSM, and the Relative Cooling Power (RCP) which is a measure of the quantity of heat which can be transferred between the hot and cold reservoirs.

However, in second order magnetic transition (SOMTs) in amorphous materials are the positive features and a low magnetic hysteresis, a high electrical resistivity, increase corrosion resistance, good mechanical properties, and an easy way of tuning TC also produce the composition variance [9]. This gives the possibility of having a broad variation entropy peak around the Curie temperature TC. In our case, magnetic studies exhibit that the Fe40Ni38Mo4B18 alloy undergoes a second order magnetic transition. For that reason, we focus in this paper on the magnetic and magnetocaloric properties around second order magnetic transition (SOMT) of amorphous Fe40Ni38Mo4B18 alloy. We have used the Arrott plots, and landau theory applied above Curie temperature (Tc) to investigate the magnetic nature, the magnetization behavior around it. We also applied a phenomenological model to predict the magnetocaloric properties.

Section snippets

Experimental details

Amorphous Fe40Ni38Mo4B18 alloys were fabricated using melt spinning in argon atmosphere. The starting material purity was better than 4 N. The obtained ribbon samples have a thickness of around 30 ± 5 μm with corresponding widths changing from 3 to 4 mm. The amorphous nature of samples was confirmed from X-ray diffraction (XRD) measurements (Fig. 1). The chemical composition was checked by electron probe microanalysis. Magnetization measurements were carried out using extraction method with a

Results and discussion

The temperature dependence of magnetization M(T) for the Fe40Ni38Mo4B18 alloy was measured under an applied field of 0.05 T in a temperature range of 315–665 K as shown in Fig. 2. It reveals the presence of a ferromagnetic (FM) to paramagnetic (PM) transition at TC = 610 K, this implies an inflection point of dM/dT(T) curve inset in Fig. 2. In order to investigate the nature of the magnetic phase transition and its correlation with the magnetocaloric effect, we have used the Inoue–Shimizu s–d

Conclusion

In summary, the x-ray diffraction (XRD) technique has confirmed the amorphous structure of the sample. We have investigated the magnetic and magnetocaloric properties of Fe40Ni38Mo4B18 alloy. Magnetic measurements have displayed the appearance of a ferromagnetic (FM) to paramagnetic (PM) transition at TC = 610 K. Based on the Landau theory and Banerjee's criterion, the sample undergoes a second-order magnetic phase transition. In addition, it is found that the maximum magnetic entropy value of

Authorship contributions

The specific contributions made by each author are: Conception and design of study: S. El Ouahbi, H. Lassri, A. Charkaoui. Acquisition of data: S. El Ouahbi, H. Lassri, L.H. Omari, E.K. Hlil, M. Sajieddine. Analysis and/or interpretation of data: S. El Ouahbi, H. Lassri, R. Moubah, Z. Yamkane, S. Derkaoui.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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