scholarly journals HIGHLY ANISOTROPIC MnBi MAGNETS

2018 ◽  
Vol 54 (1A) ◽  
pp. 58
Author(s):  
Nguyen Van Vuong
Keyword(s):  
Permanent Magnets ◽  
Spontaneous Magnetization ◽  
Mass Density ◽  
Thermal Coefficient ◽  
Energy Product ◽  
Intrinsic Coercivity ◽  
Oriented Parallel ◽  
Two Parameters ◽  
Bulk Magnet ◽  
Compacting Pressure

The rare-earth-free MnBi magnetic material is promising for high-temperature (150 200 oC) application of permanent magnets because of its large magnetocrystalline energy and especially the positive thermal coefficient of coercivity (dHc/dT > 0). Because of the moderate value of the spontaneous magnetization Ms 74 emu/g, the anisotropy of MnBi bulk magnets should be investigated to enhance the remanence Mr. With large ratio Mr/Ms and appropriate microstructure, the squareness of MnBi magnets should have high value leading the remanent coercivity bHc close to the intrinsic coercivity iHc, thus enhancing the energy product (BH)max. The paper presents an approach to loading and compacting of MnBi powders in the 18 kOe magnetic field oriented perpendicular to the pressing direction where MnBi grains can be freely rotated and oriented parallel to the field direction. Based on the energy minimization of the assembly of magnetized grains, the compacting pressure was chosen to optimize two parameters, the mass density and the coercivity iHc of magnets. The prepared MnBi bulk magnet had 8.4 g/cm3, Mr/Ms 0.92, 0.89 and (BH)max reached 8.4 MGOe.

Microstructure Of Fe-Nd-B Alloys Tailored To Approach Theoretical Coercrvtty Limits

1999 ◽  
Vol 5 (S2) ◽  
pp. 26-27
Author(s):  
Kannan M. Krishnan ◽  
Er. Girt ◽  
E. C. Nelson ◽  
G. Thomas ◽  
Ferdinand Hofer
Keyword(s):  
Magnetic Particles ◽  
Permanent Magnets ◽  
Spontaneous Magnetization ◽  
Particle Interaction ◽  
Maximum Energy ◽  
Interacting Particles ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Oriented Samples ◽  
The Difference

Performance of permanent magnets for a variety of applications is often determined by the maximum energy product (BH)max. In order to obtain high (BH)max permanent magnetic materials have to have large coercivity. In theory the coercive field of ideally oriented, non-interacting, single domain, magnetic particles, assuming Kl is much bigger than K2, was shown to be He = 2K1/Ms - N Ms, where Kl and K2 are the magnetocrystalline anisotropy constants, Ms is the spontaneous magnetization and N is the demagnetization factor. For randomly oriented non-interacting particles the Stoner-Wohlfarth model predicts that the value of Hc decreases to about half. However, experimentally obtained values of the coercitive fields in permanent magnets are 3 to 10 and 2 times smaller for well oriented and randomly oriented samples, respectively. This discrepancy was attributed to inter-particle interaction and the microstructure of the permanent magnets. In order to understand the difference between the theoretically predicted and experimentally obtained results for He we prepared rapidly quenched, Nd-rich, NdxFe14B (2 < x < 150) ribbons.

Study on the Nanostructure and Magnetic Properties of NdFeNbB Permanent Magnets

2010 ◽  
Vol 638-642 ◽  
pp. 1749-1754
Author(s):  
X.F. Wang ◽  
X.Y. Chen ◽  
Z.L. Jiang ◽  
Y. Chen ◽  
H.M. Chen
Keyword(s):  
Exchange Coupling ◽  
Permanent Magnets ◽  
Coupling Effect ◽  
Maximum Energy ◽  
Soft Magnetic ◽  
Magnetic Phases ◽  
Maximum Energy Product ◽  
Energy Product ◽  
High Maximum ◽  
Intrinsic Coercivity

Nd2Fe14B/-Fe nanocomposite permanent magnet contains the hard and soft magnetic phases, Nd2Fe14B and -Fe respectively. An exchange coupling effect exists between the two magnetic phases. The effect of alloying element Nb on its nanostructure and properties have been studied. Adding Nb to the alloy is effective to refine grains, a relatively small grain size causes a high intrinsic coercivity, remanence and therefore a high maximum energy product, (BH)max. MFM (Magnetic Force Microscope) was used to observe the magnetic micro-domain structure in the nanophase alloys. The length of the magnetic contrast shows a significant dependence on the microstructure and phase constitution, and the longer length is correspond with the larger exchange coupling effect between the soft and hard magnetic phases.

Magnetic hardening mechanism in sintered R–Fe–B permanent magnets

1988 ◽  
Vol 3 (1) ◽  
pp. 45-54 ◽  
Author(s):  
M. Sagawa ◽  
S. Hirosawa
Keyword(s):  
Temperature Dependence ◽  
Permanent Magnets ◽  
Spontaneous Magnetization ◽  
Short Review ◽  
Experimental Results ◽  
Surface Conditions ◽  
Hardening Mechanism ◽  
Intrinsic Coercivity ◽  
Field Coefficient ◽  
Magnetic Hardening

After a short review on temperature dependence of the intrinsic coercivity in sintered Nd–Fe–B-type magnets is given, recent experimental results concerning the coercivity-anisotropy (HC–HA) correlation in B-rich Pr–Fe–B and Nd–Fe–B sintered magnets and the influence of the surface conditions of the sintered Nd–Fe–B magnets on the coercivity are reported. The results are interpreted in terms of the μoHc vs cμoHA – NIs plot, where Is is the spontaneous magnetization of R2Fe14B (R = Pr or Nd) and N is the effective demagnetization field coefficient.

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.

Packing fraction dependence of the coercivity and the energy product in nanowire based permanent magnets

2013 ◽  
Vol 114 (14) ◽  
pp. 143902 ◽  
Author(s):  
Ioannis Panagiotopoulos ◽  
Weiqing Fang ◽  
Frédéric Ott ◽  
François Boué ◽  
Kahina Aït-Atmane ◽  
...  
Keyword(s):  
Permanent Magnets ◽  
Packing Fraction ◽  
Energy Product

Bulk Nanocrystalline Permanent Magnets by Selective Laser Melting

2021 ◽  
Vol 58 (10) ◽  
pp. 630-643
Author(s):  
F. Trauter ◽  
J. Schanz ◽  
H. Riegel ◽  
T. Bernthaler ◽  
D. Goll ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Field Strength ◽  
Selective Laser Melting ◽  
Permanent Magnets ◽  
Maximum Energy ◽  
Laser Melting ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Bulk Nanocrystalline ◽  
Micrometer Scale

Abstract Fe-Nd-B powders were processed by additive manufacturing using laboratory scale selective laser melting to produce bulk nanocrystalline permanent magnets. The manufacturing process was carried out in a specially developed process chamber under Ar atmosphere. This resulted in novel types of microstructures with micrometer scale clusters of nanocrystalline hard magnetic grains. Owing to this microstructure, a maximum coercive field strength (coercivity) μ0Hc of 1.16 T, a remanence Jr of 0.58 T, and a maximum energy product (BH)max of 62.3 kJ/mm3could, for example, be obtained for the composition Nd16.5-Pr1.5-Zr2.6-Ti2.5-Co2.2-Fe65.9-B8.8.

scholarly journals High-Throughput Screening of Rare-Earth-Lean Intermetallic 1-13-X Compounds for Good Hard-Magnetic Properties

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1096 ◽  
Author(s):  
Georg Krugel ◽  
Wolfgang Körner ◽  
Daniel F. Urban ◽  
Oliver Gutfleisch ◽  
Christian Elsässer
Keyword(s):  
Rare Earth ◽  
High Throughput ◽  
High Throughput Screening ◽  
Spontaneous Magnetization ◽  
Anisotropy Field ◽  
Structure Type ◽  
Anisotropy Constant ◽  
Maximum Energy ◽  
Maximum Energy Product ◽  
Energy Product

By computational high-throughput screening, the spontaneous magnetization M s , uniaxial magnetocrystalline anisotropy constant K 1 , anisotropy field H a , and maximum energy product ( B H ) max are estimated for ferromagnetic intermetallic phases with a tetragonal 1-13-X structure related to the LaCo 9 Si 4 structure type. For SmFe 13 N, a ( B H ) max as high as that of Nd 2 Fe 14 B and a comparable K 1 are predicted. Further promising candidates of composition SmFe 12 AN with A = Co, Ni, Cu, Zn, Ga, Ti, V, Al, Si, or P are identified which potentially reach (BH) max values higher than 400 kJ/m 3 combined with significant K 1 values, while containing almost 50% less rare-earth atoms than Nd 2 Fe 14 B.

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.

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