Investigation of Magnetic Behavior of SmCo5/SmCo2 Nanocrystalline Magnets

2013 ◽  
Vol 303-306 ◽  
pp. 2644-2647
Author(s):  
Li Ya Li ◽  
Jian Hong Yi ◽  
Ai Kun Li ◽  
Yuan Dong Peng
Keyword(s):  
Exchange Coupling ◽  
Melt Spinning ◽  
Domain Walls ◽  
Coupling Effect ◽  
Magnetic Behavior ◽  
Secondary Phase ◽  
Wheel Speed ◽  
Magnetization Curves ◽  
Pinning Of Domain Walls ◽  
Magnetization Processes

Nanocrystalline magnets (SmCo5)94(Cr3C2)6 were prepared using melt-spinning and their magnetic behaviors were investigated by studying their structures and magnetic properties. The alloys prepared using rapid solidification consisted of SmCo5 matrix phase, MgCu2-type SmCo2 secondary phase, and small traces of Sm2Co7 phase. The solidification with higher wheel speed were found to be preferable for the formation of single SmCo2 secondary phase. Relatively high coercive values of 28–36 kOe and high reduced remanence of 0.78–0.79 were observed for the SmCo5/SmCo2 nanocrystalline magnets. The shape of the corresponding magnetization curves revealed that two magnetization processes, nucleation and pinning of domain walls, took place in these magnets. The Henkel plots indicated strong inter-grain exchange coupling effect in these ribbons, consequently resulted in the phenomena of domains interacting with each other and enhancement of the remanence in the ribbons.

Magnetic Properties and Magnetization Reversal of Sm–Co(3x nm)/Co(x nm) Multilayered Films

2004 ◽  
Vol 19 (3) ◽  
pp. 786-794 ◽  
Author(s):  
Cai-Yin You ◽  
ChoongJin Yang ◽  
Z.D. Zhang ◽  
JongSoo Han ◽  
X.K. Sun
Keyword(s):  
Magnetic Field ◽  
Layer Thickness ◽  
Exchange Coupling ◽  
Domain Walls ◽  
Rf Sputtering ◽  
Fixed Ratio ◽  
Magnetic Interaction ◽  
Multilayered Films ◽  
Different Thickness ◽  
Pinning Of Domain Walls

[Sm–Co (3x nm) /Co (x nm)]10 (x = 10, 7, 4) multilayered films have been prepared by magnetron rf-sputtering. It is found that the thickness of both hard and soft layers has important effects on phase transformation and magnetic interaction of films. With a fixed ratio of hard- to soft-layer thickness, decreasing simultaneously the thickness of these layers results in increasing coercivity. The effects of the external magnetic field during annealing depend on the Co-layer thickness (x value), mainly because of the formation of different main phases for different thickness of Co layer. For the films with x = 10 and 7, the main phase is Sm2Co17 after annealed. Applying a magnetic field during annealing promotes the crystallization of films, and therefore, it increases the coercivity of the films with x = 10 and 7. Magnetic interaction has been investigated by measuring δm and remanence magnetization. All the films show that although the exchange coupling favorable for magnetization is significant, the increase of the coercivity mainly originates from improving the pinning effects. Temperature dependence of the coercivity supports that the pinning of domain-walls constitutes a control mechanism of the coercivity. This behavior can be well understood in terms of the Gaunt’s approach of the coercivity.

A Study of Exchange-Coupling Effect on Nd2Fe14B / α-Fe Forming Core/Shell Shape

2007 ◽  
Vol 119 ◽  
pp. 147-150 ◽  
Author(s):  
Chang Woo Kim ◽  
Young Hwan Kim ◽  
Don Keun Lee ◽  
In Chul Jeong ◽  
Hae Woong Kwon ◽  
...  
Keyword(s):  
Exchange Coupling ◽  
Ball Mill ◽  
Coupling Effect ◽  
Chemical Reduction ◽  
High Energy ◽  
Shell Shape ◽  
Core Shell ◽  
High Energy Ball Mill ◽  
Energy Ball ◽  
Mill Process

We report the core/shell type as the interesting one of the various techniques to prepare exchange-coupled permanent magnet. In this study, the exchange-coupled Nd2Fe14B/α-Fe was prepared by high energy ball mill process and chemical reduction. Nd15Fe77B8 powder prepared by high energy ball mill process was coated with α-Fe nanoparticle by chemical reduction. α-Fe nanoparticle on the ball milled Nd15Fe77B8 was synthesized by chemical reduction with borohydride as a reducing agent in aqueous solution. After annealing, Nd2Fe14B/α-Fe forming core/shell shape has exchange-coupling effect and was identified by using XRD, FE-SEM, VSM, TMA and EDX.

scholarly journals Flux Mapping and Magnetic Behavior of Grain Boundaries in Nd-Fe-B Magnets

1999 ◽  
Vol 589 ◽  
Author(s):  
V.V. Volkov ◽  
Yimei Zhu
Keyword(s):  
Magnetic Flux ◽  
Grain Boundaries ◽  
Domain Walls ◽  
Quantitative Description ◽  
Magnetic Behavior ◽  
Local Variation ◽  
Smooth Transition ◽  
Lorentz Microscopy ◽  
Hard Magnets

AbstractAdvanced Fresnel- & Foucault-Lorentz microscopy were applied to analyze magnetic behavior of the grain boundaries in Nd-Fe-B hard magnets. In-situ TEM magnetizing experiments combined with these imaging methods revealed the process of magnetization reversal in polycrystalline sintered and die-upset Nd-Fe-B under various magnetic fields. Fine details of magnetic flux distribution, derived from the magnetic interferograms created by phase-coherent Foucault imaging, provide a quantitative description of the local variation of magnetic flux. Our study suggests that the grain boundaries play an important multi-functional role in the reversal of magnetization, by acting as (a) pinning centers of domain walls, (b) centers of nucleation of reversal domains, and (c) sinks or sources for migrating magnetostatic charges and/or dipoles. They also ensure a smooth transition for irreversible remagnetization in polycrystalline samples.

scholarly journals STRUCTURAL CHARACTERIZATION OF THE NEW DIAMOND-LIKE SEMICONDUCTOR CuNbGaSe3

2018 ◽  
Vol 15 (29) ◽  
pp. 228-233
Author(s):  
J. A. FLORES-CRUZ ◽  
G. E. DELGADO ◽  
J. E. CONTRERAS ◽  
M. QUINTERO ◽  
L. NIEVES ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Magnetic Behavior ◽  
Secondary Phase ◽  
Chalcopyrite Structure ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Chalcogenide Compound ◽  
Semiconductor Type

The chalcogenide compound CuNbGaSe3, belonging to the system I-II-III-VI3, has been investigated by means of X-ray powder diffraction and its crystal structure has been refined by the Rietveld method.This is a material of the semiconductor type, which improves the properties of a simple semiconductor like CuGaSe2 because it ads spintronic applications due to its magnetic behavior. The powder pattern was composed by 94.2% of the principal phase CuNbGaSe3 and 5.8% of the secondary phase Cu0.667NbSe2. This material crystallizes with a CuFeInSe3-type structure in the tetragonal space group P4 2c (Nº 112), unit cell parameters a = 5.6199(4) Å, c = 11.0275(2) Å, V = 348.28(4) Å3, with a normal adamantane-structure where occurs a degradation of symmetry from the chalcopyrite structure I4 2d to a related structure P4 2c.

Microstructure Analysis of Melt-Spun Al3Ti Intermetallics by XRD and EXAFS

1996 ◽  
Vol 460 ◽  
Author(s):  
Jinmin Chen ◽  
W. E. Frazier ◽  
E. V. Barrera
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Melt Spinning ◽  
Composition Range ◽  
Processing Parameters ◽  
Wheel Speed ◽  
Annealing Temperatures ◽  
Melt Spun ◽  
Temperature Heat ◽  
Spinning Process

ABSTRACTIn an effort to expand the composition range over which Al3Ti is stable, various amounts of niobium were substituted for titanium and processed by melt-spinning. Several samples were annealed both at 600°C and 1000°C for 24 hours. The effects of processing parameters such as wheel speed, the amount of niobium, and annealing temperatures on the structure were investigated by XRD and EXAFS. XRD showed that for all the samples the only structure present was DO22-The DO22 structure was stable even after the high temperature heat treatments. By means of EXAFS, niobium atoms were observed to occupy titanium sites in the DO22 structure. Furthermore, in the unannealed samples, increasing wheel speed of the melt spinning process or the niobium concentration tended to distort the crystal structure. It was observed that Ti EXAFS had different results from the Nb EXAFS beyond their occupying similar sites, which suggested there may exist some composition zones, i.e. rich Nb zone or rich Ti zones, although the structures present were still DO22. The samples were found to experience different distortions as a function of annealing temperatures.

Influence of Co-Doping on Magnetic Properties and Magnetocaloric Effect of Fe–Co–Zr–Cu–B Melt-Spun Ribbons

2021 ◽  
Vol 21 (4) ◽  
pp. 2552-2557
Author(s):  
Nguyen Hai Yen ◽  
Nguyen Hoang Ha ◽  
Pham Thi Thanh ◽  
Nguyen Huy Ngoc ◽  
Tran Dang Thanh ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetocaloric Effect ◽  
Melt Spinning ◽  
Room Temperature ◽  
Tangential Velocity ◽  
Magnetic Behavior ◽  
Entropy Change ◽  
Co Doping ◽  
Melt Spun ◽  
Melt Spun Ribbons

In this work, we investigated magnetic properties and magnetocaloric effect in Fe90−xCoxZr7Cu1B2 (x = 0, 1, 2, 3 and 4) melt-spun ribbons. The ribbons were prepared by using a melt-spinning method with a tangential velocity of a copper wheel of 40 m·s-1. The obtained ribbons are almost amorphous. The alloys exhibit typical soft magnetic behavior with low coercivity at room temperature. A minor replacement of Fe by Co gives an increment in Curie temperature (TC) of the alloys to higher temperatures. The TC of the alloys increases from 242 to 342 K with an increase of x from 0 to 4. Maximum magnetic entropy change, ΔSm max, of the alloys, was found to be larger than 0.7 J·kg-1·K-1 in a magnetic field change ΔH of 12 kOe for all the concentrations of Co. High refrigerant capacitys (RC >100 J ·kg-1 with ΔH = 12 kOe) at room temperature region have been obtained for the alloys. The large magnetocaloric effect near room temperature suggests that the alloys can be considered as magnetic refrigerants in the range of 250–350 K.

A Study of Exchange-Coupling Effect on Nd2Fe14B / α-Fe Forming Core/Shell Shape

2007 ◽  
pp. 147-150
Author(s):  
Chang Woo Kim ◽  
Young Hwan Kim ◽  
Don Keun Lee ◽  
In Chul Jeong ◽  
Hae Woong Kwon ◽  
...  
Keyword(s):  
Exchange Coupling ◽  
Coupling Effect ◽  
Shell Shape ◽  
Core Shell
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