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.

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.

Microstructure and hard magnetic properties of nanocomposite Sm2Fe15Ga2Cx permanent magnets with an excess of Fe prepared directly by melt spinning

1998 ◽  
Vol 72 (9) ◽  
pp. 1110-1112 ◽  
Author(s):  
Zhao-hua Cheng ◽  
Jun-xian Zhang ◽  
Hui-qun Guo ◽  
J. van Lier ◽  
H. Kronmüller ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Melt Spinning ◽  
Permanent Magnets ◽  
Hard Magnetic Properties

Improved thermal stability of hard magnetic properties in rapidly solidified RE–TM–B alloys

2008 ◽  
Vol 23 (10) ◽  
pp. 2733-2742 ◽  
Author(s):  
Z.W. Liu ◽  
R.V. Ramanujan ◽  
H.A. Davies
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Magnetic Properties ◽  
Elevated Temperature ◽  
Melt Spinning ◽  
Maximum Energy ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Rapidly Solidified ◽  
Hard Magnetic Properties

Rapidly solidified nanocrystalline RE–TM–B (RE = Nd, Pr, Dy, TM = Fe, Co) alloys with enhanced hard magnetic properties were synthesized by melt spinning. The composition- and microstructure-dependent elevated temperature magnetic properties were investigated. The temperature coefficients of remanence (α) and coercivity (β) were determined. The effects of Pr substituting Nd, Co substituting Fe, Dy substituting RE, and grain size on the Curie temperature and thermal stability were studied. Co or Dy substitutions were found to have a significant beneficial effect on the thermal stability. Reducing grain size could also improve elevated temperature behavior. Maximum energy product (BH)max > 100 kJ/m3 could be obtained in compositionally optimized nanophase alloys at temperature of 473 K. Extremely low coefficients of α and β were realized in exchange coupled nanocomposite alloys. Bonded nanocomposite magnets with α = −0.052%/K and β = −0.0365%/K for 300–400 K were also successfully fabricated.

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.

EM of rapidly solidified permanent magnets

1992 ◽  
Vol 50 (1) ◽  
pp. 198-199
Author(s):  
Raja K. Mishra
Keyword(s):  
Melt Spinning ◽  
Permanent Magnets ◽  
Dark Field Image ◽  
Dark Field ◽  
Maximum Energy ◽  
Quench Rate ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Annular Dark Field ◽  
Rapidly Solidified

The discovery of a new class of permanent magnets based on Nd2Fe14B phase in the last decade has led to intense research and development efforts aimed at commercial exploitation of the new alloy. The material can be prepared either by rapid solidification or by powder metallurgy techniques and the resulting microstructures are very different. This paper details the microstructure of Nd-Fe-B magnets produced by melt-spinning.In melt spinning, quench rate can be varied easily by changing the rate of rotation of the quench wheel. There is an optimum quench rate when the material shows maximum magnetic hardening. For faster or slower quench rates, both coercivity and maximum energy product of the material fall off. These results can be directly related to the changes in the microstructure of the melt-spun ribbon as a function of quench rate. Figure 1 shows the microstructure of (a) an overquenched and (b) an optimally quenched ribbon. In Fig. 1(a), the material is nearly amorphous, with small nuclei of Nd2Fe14B grains visible and in Fig. 1(b) the microstructure consists of equiaxed Nd2Fe14B grains surrounded by a thin noncrystalline Nd-rich phase. Fig. 1(c) shows an annular dark field image of the intergranular phase. Nd enrichment in this phase is shown in the EDX spectra in Fig. 2.

The hard magnetic properties of nanocomposite Nd3.6Pr5.4Fe83Co3B5 ribbons prepared by melt spinning

2001 ◽  
Vol 304-306 ◽  
pp. 997-1000 ◽  
Author(s):  
Hong-Wei Zhang ◽  
Wen-Yong Zhang ◽  
A-Ru Yan ◽  
Zhi-Gang Sun ◽  
Bao-Gen Shen ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Melt Spinning ◽  
Hard Magnetic Properties

Effect of Dysprosium Content on the Magnetic Properties of Nanocrystalline (Pr0.25Nd0.75)10-xDyxFe82Co2B6 Alloys

2014 ◽  
Vol 789 ◽  
pp. 28-31 ◽  
Author(s):  
He Wei Ding ◽  
Chun Xiang Cui ◽  
Ji Bing Sun
Keyword(s):  
Magnetic Properties ◽  
Melt Spinning ◽  
Maximum Energy ◽  
Vibrating Sample Magnetometer ◽  
X Ray ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Intrinsic Coercivity ◽  
Electronic Microscope ◽  
Microstructure And Magnetic Properties

(Pr0.25Nd0.75)10-xDyxFe82Co2B6(x=0~0.3) ribbons were prepared by melt spinning at 25m/s and subsequent annealing. The effect of Dy content on the microstructure and magnetic properties of the ribbons has been investigated by X-ray diffractometer (XRD), scanning electronic microscope (SEM) and vibrating sample magnetometer (VSM). The magnetic properties related to the Dy content were characterized. Intrinsic coercivity of 598kA/m, remanence of 0.58T, and the maximum energy product (BH)max of 43kJ/m3 were achieved in (Pr0.25Nd0.75)9.8Dy0.2Fe82Co2B6 after annealing at 700°C for 10 minutes.

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.

Enhancement of exchange coupling and hard magnetic properties in nanocomposites by magnetic annealing

2005 ◽  
Vol 53 (15) ◽  
pp. 4155-4161 ◽  
Author(s):  
B.Z. Cui ◽  
K. Han ◽  
H. Garmestani ◽  
J.H. Su ◽  
H.J. Schneider-Muntau ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Exchange Coupling ◽  
Magnetic Annealing ◽  
Hard Magnetic Properties
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