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Smart Lightweight Polymer Composites
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Lothar Kroll, Lightweight Polymer Composite Structures, 2020
Nayan Ranjan Singha, Mousumi Deb, Manas Mahapatra, Madhushree Mitra, Pijush Kanti Chattopadhyay
Magnetic hysteresis is caused by the alignment of dipoles of a ferromagnetic material in the presence of external magnetic field, followed by the change in orientation and partial nonalignment of the dipoles, if external magnetic field is switched off. Thus, as a result of magnetic hysteresis, part of the aligned dipoles remains unaltered even after the removal of external magnetic field, whereas the remaining dipoles revert back to the unaligned condition. The material experiences energy loss during the magnetic hysteresis as a result of change in rotation of magnetization and size or number of magnetic domains formed by the similarly oriented atoms in a ferromagnetic material. The extent of magnetic hysteresis loss depends mainly on magnetic properties of material, including Rayleigh constant and permeability of material. The Rayleigh constant describes Barkhausen jumps or Barkhausen effect related to the noise in the magnetic output of a ferromagnet in fluctuating magnetic field, which is caused by rapid changes in the sizes of magnetic domains.
Magnetic Materials for Nuclear Magnetic Resonance and Magnetic Resonance Imaging
Published in Sam Zhang, Dongliang Zhao, Advances in Magnetic Materials, 2017
Elizaveta Motovilova, Shaoying Huang
The unique feature of ferromagnetic materials is that the relation between M and H is not linear. Moreover, the complicated relation between M and H for ferromagnetic materials is difficult to characterize by simple mathematic functions. Thus, it is usually obtained through a series of experiments by plotting the magnetization M against the strength H of the external magnetic field applied. A magnetic hysteresis loop is shown in Figure 3.7. Ferromagnetic materials can be easily magnetized, and in strong magnetic fields the magnetization reaches a certain limit called saturation magnetization Ms, as shown in Figure 3.7. Beyond this limit no further significant increase in magnetization occurs. It should be noted that saturation magnetization is an intrinsic property of a material, which does not depend on the shape or size of the material. Interestingly, with the gradual reduction of the applied field, the magnetization M of a ferromagnetic material does not decrease by its original path, but at a slower rate. When | H | reaches 0 A/m, M is still positive. This positive magnetization is called remanence and denoted using Mr. Therefore, unlike dia- or paramagnetic materials, ferromagnetic materials retain a magnetization after the externally applied magnetic field is removed, or in other words, they “remember” their history. This feature of ferromagnetic materials is exploited in magnetic memory devices such as magnetic tape, hard disk drives, and credit cards. When | H | is reduced further (becomes negative and changes its direction), the magnetization becomes zero again at a certain value of magnetic field strength which is called the point of coercivity and denoted by Hc. This parameter indicates the strength of the reverse field needed to remove the residual magnetization from the material after the saturation. As the field strength increases further, the magnetization reaches the saturation magnetization in the opposite direction. To complete the entire cycle, | H | along the negative direction can be moved gradually back to 0 A/m and then increased till M reaches the positive saturation magnetization. As is shown in Figure 3.7, by changing the magnetic field strength H and measuring the induced magnetization M for ferromagnetic materials, a loop, called the magnetic hysteresis loop is formed, that characterizes the unique behavior of ferromagnetic magnetization.
Super-hierarchical and explanatory analysis of magnetization reversal process using topological data analysis
Published in Science and Technology of Advanced Materials: Methods, 2022
Sotaro Kunii, Alexandre Lira Foggiatto, Chiharu Mitsumata, Masato Kotsugi
Figure 2(a) shows the magnetic hysteresis in the metastable/stable magnetization reversal processes. The metastable process is indicated by a rhombus marker, whereas the stable process is indicated by a square marker. The external magnetic field scans continuously from +0.5 to −0.5 T. It is shown that the magnetization of the nanodot reverses in the range of 0.25 to −0.25 T for both the metastable and stable processes. We focused on the region of magnetization reversal (black rectangle inset) and magnified this region, as shown in Figure 2(b). The magnetization of the metastable process changes continuously from Figures 2(c.1) to 2(c.6), while that of the stable process changes from Figure 2(d.1) to 2(d.6). The coercivity is negligible in the magnetization curve, but this is a reasonable result as the sample is composed of a soft magnetic material.
One-pot synthesis of magnetic chitosan/iron oxide bio-nanocomposite hydrogel beads as drug delivery systems
Published in Soft Materials, 2021
S. Barkhordari, A. Alizadeh, M. Yadollahi, H. Namazi
To explore the magnetic properties of the CH/MION nanocomposite hydrogel beads, the magnetization curve was determined from Vibrating Sample Magnetometer (VSM) at room temperature (300 K) Figure 3 shows the magnetization of CH/MION15 sample as a function of the magnetic field in the range of −15,000 to 15,000 Oe. The magnetization increased with an increase in the magnetic field. Moreover, the magnetic hysteresis loops are S-like curves and have no coercivity and remanence, implying that there is no remaining magnetization when the external magnetic field is removed. These results indicate that the magnetic composites exhibit typical superparamagnetic behavior, and the single-domain magnetite NPs remained in the composite. The VSM plot present values of 4.73 emu.g−1 for the saturation magnetization (Ms) of the CH/MION15 sample
Combined performance of hydroxyapatite adsorption and magnetic separation processes for Cd(II) removal from aqueous solution
Published in Journal of Dispersion Science and Technology, 2021
Xiaoxiao Shen, Xuan Gao, Wei Wei, Yong Zhang, Yong Zhang, Lili Ma, Huaji Liu, Ruiming Han, Jun Lin
A room-temperature magnetic hysteresis curve (i.e., the plot of magnetization vs. magnetic field) for the HAP modified γ-Fe2O3 nanocomposite is shown in Figure 4. The results indicated superparamagnetic properties (i.e., zero coercive field and zero remnant magnetization) of the prepared nanocomposite with the saturation magnetization (Ms) of 2.17 emu/g, which was much lower than that of pure γ-Fe2O3 materials (Ms = 50 emu/g).[43] The result of low-saturation magnetization was attributed to the diamagnetic contribution of the HAP matrix covering the γ-Fe2O3 nanoparticles. Similar findings have been reported by Cai et al.,[44] who also indicated a low-saturation magnetization (1.66 emu/g) of magnetic nanocomposite, due to the diamagnetic contribution of the SiO2 shells covering the Fe3O4 nanoparticles.