scholarly journals Enhancement of Hard Magnetic Properties in Fraktal-Like Nano and Mesoscopic Grains

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1443
Author(s):  
Grzegorz Ziółkowski ◽  
Dariusz Chrobak ◽  
Grażyna Chełkowska ◽  
Ondrej Zivotsky ◽  
Artur Chrobak
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Permanent Magnets ◽  
High Surface ◽  
Volume Ratio ◽  
High Coercivity ◽  
Energy Product ◽  
Surface Development ◽  
System Nodes ◽  
Hard Magnetic Properties

The paper refers to Monte Carlo magnetic simulations for fractal-like nano and mesoscopic grains. The analyzed objects differed in the size, surface development, magnetic anisotropy and the spin values attributed to the system nodes inside the fractal. Such an approach allowed us to determine their magnetization processes as well as optimization characteristics in the direction to enhancement of hard magnetic properties. As it was shown, the size effects depend on the chosen value of magnetic anisotropy. In the case of fractals with ultra-high coercivity, the decreasing of their size leads to deterioration of coercivity, especially for the high surface to volume ratio. Opposite effects were observed for soft magnetic fractals when the nanostructure caused an appearance of the coercive field, and the maximum of energy product was predictably significantly higher than for conventional rare earths’ free permanent magnets.

Preparation and Magnetic Properties of the Exchange Coupling NdFeB Nanocomposited Permanent Magnets

2007 ◽  
Author(s):  
Zongjun Tian ◽  
Shangdong Li ◽  
Youwei Du ◽  
Yinhui Huang
Keyword(s):  
Magnetic Properties ◽  
Hysteresis Loop ◽  
Grain Boundaries ◽  
Exchange Coupling ◽  
Melt Spinning ◽  
Permanent Magnets ◽  
Energy Product ◽  
Remanence Ratio ◽  
Optimum Energy ◽  
Hard Magnetic Properties

The effect of indium additions on the microstructures and magnetic properties of Nd9Fe85−xB6Inx (x = 0–2) nanocomposites prepared by melt spinning was investigated. It was found that a certain amount of indium added to Nd9Fe85B6 magnets enhances the hard magnetic properties. The coercivity and remanence ratio of the magnet with 0.5 at.% indium increases from 405kA/m (no indium) to 465kA/m and from 0.7 to 0.86 respectively. Squareness of its hysteresis loop is also improved greatly. The optimum energy product (BH)max increases remarkably from 95kJ/m3 to 145kJ/m3. The origin for those enhancements is mainly attributed to the magnetically softened grain boundaries and enhanced crystallographical coherency by indium addition. The magnetic annealing is found to be helpful to enhance the coherency and coupling between hard and soft phases.

HARD MAGNETIC PROPERTIES OF MULTILAYERED SmCo/Co PERMANENT MAGNETS

2001 ◽  
Vol 15 (24n25) ◽  
pp. 3243-3246 ◽  
Author(s):  
R. ANDREESCU ◽  
M. J. O'SHEA
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
High Field ◽  
Permanent Magnets ◽  
Energy Product ◽  
Field Magnetization ◽  
High Field Magnetization ◽  
Energy Products ◽  
Hard Magnetic Properties

We have prepared (Sm-Co)/Co multilayers with two different Co thicknes to study the hard magnetic properties (coercivity Hci and energy product BHmax ) of nanostructured SmCo magnets consisting of hard SmCo and softer higher moment Co phases. Samples are annealed at a temperature in the range 450 – 700°C, for 20 minutes in vacuum (standard anneal) or rapidly annealed for 30 seconds under flowing nitrogen (rapid anneal) to form the hard Sm-Co phase. We find that samples subjected to a standard anneal at 500°C or a rapid anneal at 650°C show the largest energy products in these thin films, about 21 MG.Oe. This is closely related to the fact that the high field magnetization is highest for these anneal temperatures and decreases at higher anneal temperatures.

Preparation and magnetic properties of bulk nanostructured PrCo5 permanent magnets with strong magnetic anisotropy

2011 ◽  
Vol 109 (7) ◽  
pp. 07A731 ◽  
Author(s):  
W. Q. Liu ◽  
J. H. Zuo ◽  
M. Yue ◽  
W. C. Lv ◽  
D. T. Zhang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Permanent Magnets

Structure and Magnetic Properties of Heat-Resistant Sm(Co0.796−xFe0.177CuxZr0.027)6.63 Permanent Magnets with High Coercivity

JOM ◽  
2018 ◽  
Vol 71 (2) ◽  
pp. 559-566 ◽  
Author(s):  
A. G. Popov ◽  
V. S. Gaviko ◽  
V. V. Popov ◽  
O. A. Golovnia ◽  
A. V. Protasov ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Permanent Magnets ◽  
High Coercivity ◽  
Heat Resistant

scholarly journals Magnetic Properties, Adhesion, and Nanomechanical Property of Co40Fe40W20 Films on Si (100) Substrate

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Wen-Jen Liu ◽  
Yung-Huang Chang ◽  
Sin-Liang Ou ◽  
Yuan-Tsung Chen ◽  
You-Cheng Liang ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Surface Energy ◽  
Resonance Frequency ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
High Surface ◽  
Contact Angles ◽  
Thickness Effect ◽  
High Coercivity ◽  
High Surface Energy

In this study, a Co40Fe40W20 alloy was sputtered onto Si (100) with thicknesses (tf) ranging from 18 to 90 nm, and the corresponding structure, magnetic properties, adhesive characteristics, and nanomechanical properties were investigated. X-ray diffraction (XRD) patterns of the Co40Fe40W20 films demonstrated a significant crystalline body-centered cubic (BCC) CoFe (110) structure when the thickness was 42 nm, and an amorphous status was shown when the thickness was 18 nm, 30 nm, 60 nm, and 90 nm. The saturation magnetization (Ms) showed a saturated trend as tf was increased. Moreover, the coercivity (Hc) showed a minimum 1.65 Oe with 30 nm. Hc was smaller than 4.5 Oe owing to the small grain size distribution and amorphous structure, indicating that the Co40Fe40W20 film had soft magnetism. The low-frequency alternating current magnetic susceptibility (χac) decreased as the frequency was increased. The χac revealed a thickness effect when greater thicknesses had a large χac. The maximum χac and optimal resonance frequency (fres) of Co40Fe40W20 were investigated. The maximum χac indicated the spin sensitivity and was maximized at the optimal resonance frequency. The 90 mm thickness had the highest χac 0.18 value at an fres of 50 Hz. The contact angles of the Co40Fe40W20 films are less than 90°, which indicated that the film had a good wetting effect and hydrophilicity. The surface energy was correlated with the adhesion and displayed a concave-down trend. CoFeW films can be used as a seed or buffer layer; therefore, the surface energy and adhesion are very important. The highest surface energy was 30.12 mJ/mm2 at 42 nm and demonstrated high adhesion. High surface energy has corresponding strong adhesive performance. The increased surface roughness can induce domain wall pinning effect and high surface energy, causing a high coercivity and strong adhesion. The increase of hardness and Young’s modulus could be reasonably inferred from the thinner CoFeW films. The hardness and Young’s modulus of CoFeW films are also displayed to saturated tendency when increasing thickness.

High Magnetic Field Annealing of Mn-Ga Intermetallic Alloys

MRS Advances ◽  
2015 ◽  
Vol 1 (3) ◽  
pp. 227-233 ◽  
Author(s):  
Daniel R. Brown ◽  
Ke Han ◽  
Theo Siegrist ◽  
Tiglet Besara ◽  
Rongmei Niu
Keyword(s):  
Magnetic Field ◽  
Heat Treatment ◽  
Magnetic Properties ◽  
Permanent Magnets ◽  
Intermetallic Alloys ◽  
Nanostructured Composite ◽  
Refined Microstructure ◽  
Field Annealing ◽  
High Magnetic Moment ◽  
Hard Magnetic Properties

AbstractMn-Ga alloys have shown promising hard magnetic properties, even though these alloys contain no rare-earth metals. However, much work is needed before Mn-Ga alloys become viable permanent magnets for applications. One of the challenges is to enhance the remanence. One technique to improve this property is applying a magnetic field during the heat treatment process. Magnetic annealing can promote phase transformation of the phases with high magnetic moment. This results in an increased remanence. Bulk samples of Mn-Ga alloys were made by mechanically alloying in order to create a nanostructured composite, followed by heat treatments in the presence of a 31 T magnetic field. The heat treatment temperatures were kept low in order to keep the refined microstructure. All the alloys exhibit hard magnetic properties at room temperature with large coercivity. This work reports findings of magnetic field annealed Mn-Ga bulk that exhibit high coercivities up to 19.4 kOe and increased remanence of 50% over the binary system, achieving values up to 6.9 emu/g. This is the highest coercivity reported in bulk Mn-Ga samples.

scholarly journals Microstructure and Magnetic Properties of Ce14Fe78Co2B6 Nanopowders Prepared by Ball Milling at Low Temperature

2021 ◽  
Vol 7 (12) ◽  
pp. 160
Author(s):  
Marian Grigoras ◽  
Mihaela Lostun ◽  
Firuta Borza ◽  
Marieta Porcescu ◽  
George Stoian ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Low Temperature ◽  
Ball Milling ◽  
Liquid Nitrogen ◽  
High Performance ◽  
Permanent Magnets ◽  
X Ray Diffraction ◽  
Hard Magnetic Properties ◽  
Uniform Particle Size ◽  
Microstructure And Magnetic Properties

Ce14Fe78Co2B6 nanopowders with hard-magnetic properties have been successfully prepared by ball milling at low temperatures in liquid nitrogen. The morphology, structure, and magnetic properties of Ce14Fe78Co2B6 powders have been investigated using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. It was found that powder ball milling at low temperature in liquid nitrogen, has the advantage that the oxidation of powders is inhibited and the particles rapidly reach nanometric dimensions. In comparison to the Ce14Fe78Co2B6 powders prepared by ball milling at room temperature, the powders milled at low temperature present a more uniform particle size and no rare-earth oxides, which leads thus to remarkable magnetic properties. The nanocrystalline Ce14Fe78Co2B6 powders with optimum characteristics, prepared at low temperature, have the size of 153 nm or less, present a coercivity of 5.1 kOe, and a saturation magnetization of 113 emu/g after milling for 6 h at low temperature. Low temperature milling may become a promising technique for the fabrication of high performance powders used for permanent magnets preparation.

scholarly journals Development of a High-Performance-Ferrite Magnet Fabrication Process without Sintering Additives

2021 ◽  
Vol 59 (8) ◽  
pp. 551-559
Author(s):  
Pyeong-Yeol Yu ◽  
Min-Ho Kim ◽  
Young-Min Kang
Keyword(s):  
Magnetic Properties ◽  
Saturation Magnetization ◽  
High Performance ◽  
Secondary Phase ◽  
Batch Process ◽  
Maximum Energy ◽  
Magnetic Flux Density ◽  
Sintering Additives ◽  
Energy Product ◽  
Hard Magnetic Properties

Sintered M-type hexaferrites with the chemical formula of Sr0.3Ca0.4La0.3Fe9.8Co0.2-xMnxSi0.135O19-d (x = 0, 0.05, 0.1, 0.2) and Sr0.3Ca0.4La0.3Fe9.8-yCo0.2MnySi0.135O19-d (y = 0.05, 0.1, 0.2) were prepared by conventional solid station reaction routes. A high sintering density of more than 95% of the theoretical density was achieved in all hexaferrite samples when calcination was carried out at 1100 oC for 4 h, followed by sintering at 1230-1250 oC for 2 h without the use of sintering additives. High saturation magnetization and coercivity were achieved simultaneously at the x = 0.05 composition, where Mn replaces part of the Co. The secondary phase Fe2O3 generated by the initial addition of SiO2 was gradually reduced when the Fe contented was decreased in the Sr0.3Ca0.4La0.3Fe9.8-zCo0.15Mn0.05Si0.135O19-d samples, and a single M-type hexaferrite phase was confirmed in the Sr0.3Ca0.4La0.3Fe8.3Co0.15Mn0.05Si0.135O19-d (z = 1.5) sample, which also exhibited optimized hard magnetic properties, with a saturation magnetization of 4581 G and coercivity of 4771 Oe. Anisotropic sintered magnets were fabricated using the optimized composition, and showed excellent hard magnetic properties, with a remanent magnetic flux density of 4400 G and intrinsic coercivity of 4118 Oe, and a maximum energy product of 4.72 M·G·Oe. This result is very promising because high magnet performance can be achieved with a single batch process without the need for sintering additives during the process.

Magnetic anisotropy of Sm2Fe17−xGax hydrides

1993 ◽  
Vol 71 (11-12) ◽  
pp. 574-577 ◽  
Author(s):  
R. A. Dunlap ◽  
Z. Wang
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Room Temperature ◽  
Single Phase ◽  
Easy Axis ◽  
Phase 2 ◽  
Planar Anisotropy ◽  
Uniaxial Magnetic Anisotropy ◽  
Diffusion Of Hydrogen ◽  
Hard Magnetic Properties

The magnetic properties of single-phase 2:17 compounds of the composition Sm2Fe17−xGaxHy were investigated. The substitution of Ga for Fe in the Sm2Fe17 compound resulted in a substantial increase in the Curie temperature and, for alloys with x > 2, the formation of a uniaxial magnetic anisotropy at room temperature. The diffusion of hydrogen into those compounds that exhibit an easy axis anisotropy causes a transition back to a planar anisotropy. This indicates that the presence of interstitial hydrogen is detrimental to the hard magnetic properties of these materials.

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