Magnetic Properties of Polymer Bonded Exchange-Spring NdFeB Magnets

1999 ◽  
Vol 577 ◽  
Author(s):  
B. Mokal ◽  
N.A. Smith ◽  
A.J. Williams ◽  
I.R. Harris
Keyword(s):  
Magnetic Properties ◽  
Exchange Coupling ◽  
Volume Fraction ◽  
Exchange Interactions ◽  
Soft Materials ◽  
Soft Phase ◽  
Fine Grain ◽  
Milled Material ◽  
Melt Spun ◽  
Final Composition

ABSTRACTThe production of remanence enhanced powders, using a method of mechanical alloying of free iron to melt spun ribbon, has been studied. The final composition is Nd8. 1Fe77.1Co10.9B3.9 and both hard and soft materials possess an initial fine grain size; approximately 30nm for the Nd2Fe14B phase in the melt spun ribbon and 1µm for the α-Fe. The magnetic properties of resin bonded magnets fabricated using such material have been measured and found to exhibit exchangespring behaviour. The experiments performed in this work are described with respect to the volume fraction of the soft phase and subsequent annealing temperature of the as-milled material. Remanence enhancement has been observed and this can be attributed to the exchange interactions between the ferromagnetic soft and hard phases. For a 30% by volume addition of α-Fe, typical values of remanence were found to be ∼880mT with a coercivity of ∼250 kA/m. The reversible and irreversible components of the magnetisation have been determined, to demonstrate the exchange coupling and coercivity behaviours respectively.

PHASE EVOLUTION AND MAGNETIC PROPERTIES OF TbCu7-TYPE (Sm, Pr)Co7-xHfxMy (x = 0-0.5; y = 0-0.14) RIBBONS

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1663-1669 ◽  
Author(s):  
H. W. Chang ◽  
S. T. Huang ◽  
I. W. Chen ◽  
C. W. Chang ◽  
W. C. Chang
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Exchange Coupling ◽  
Coupling Effect ◽  
Anisotropy Field ◽  
Phase Evolution ◽  
Phase Constitution ◽  
Melt Spun

The effects of Hf substitution and C content on the magnetic properties, phase evolution, and microstructure of melt spun ( Sm , Pr ) Co 7- x Hf x C y ( x = 0-0.5; y = 0-0.14) ribbons have been studied. A proper Hf substitution is helpful not only in stabilizing 1:7 phase but also in enhancing its magnetic anisotropy field. As a result, magnetic properties of B r = 6.4 kG , i H c = 7.3 kOe and ( BH ) max = 8.7 MGOe for SmCo 6.9 Hf 0.1 ribbons are obtained. Besides, a small amount of C addition in the ribbons could slightly modify phase constitution and effectively refine their microstructure to strengthen the exchange coupling effect between magnetic grains. Furthermore, a slight Pr substitution for Sm may further increase the magnetization and the magnetic properties of the ribbons. The optimal magnetic properties of B r = 7.1 kG , i H c = 8.5 kOe and ( BH ) max = 11.2 MGOe could be achieved for the directly quenched Sm 0.8 Pr 0.2 Co 6.9 Hf 0.1 C 0.12 ribbons.

HIGH MAGNETIC PROPERTIES OF TbCu7-TYPE MELT SPUN (Sm, Pr)Co7-xHfxCy RIBBONS

2008 ◽  
Vol 01 (03) ◽  
pp. 183-187 ◽  
Author(s):  
H. W. CHANG ◽  
S. T. HUANG ◽  
I. W. CHEN ◽  
C. W. CHANG ◽  
W. C. CHANG
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Exchange Coupling ◽  
Coupling Effect ◽  
Anisotropy Field ◽  
Phase Evolution ◽  
Phase Constitution ◽  
Melt Spun

The effects of Hf substitution and C content on the magnetic properties, phase evolution and microstructure of melt spun ( Sm , Pr ) Co 7-x Hf x C y (x = 0–0.5; y = 0–0.14) ribbons have been studied. A proper Hf substitution is helpful not only in stabilizing 1:7 phase but also in enhancing its magnetic anisotropy field, as a result, magnetic properties of B r = 6.4 kG , i H c = 7.3 kOe and (BH) max = 8.7 MGOe for SmCo 6.9 Hf 0.1 ribbons are obtained. Besides, a small amount of C addition in the ribbons could slightly modify phase constitution and effectively refine their microstructure to strengthen the exchange coupling effect between magnetic grains. It leads to the improvement of the magnetic properties for SmCo 6.8 Hf 0.2 C 0.12 nanocomposites. Finally, a slight Pr substitution for Sm may further increase the magnetization and the magnetic properties, the optimal magnetic properties of B r = 7.1 kG , i H c = 8.5 kOe and (BH) max = 11.2 MGOe could be achieved for the directly quenched Sm 0.8 Pr 0.2 Co 6.9 Hf 0.1 C 0.12 ribbons.

A Study of Exchange Interactions in R(FeCo)11TiCy (R=Y or Pr) Compounds

2011 ◽  
Vol 170 ◽  
pp. 223-226
Author(s):  
Corneliu Bazil Cizmas ◽  
Lotfi Bessais
Keyword(s):  
Magnetic Properties ◽  
Exchange Interaction ◽  
Magnetic Moment ◽  
Exchange Coupling ◽  
Interaction Strength ◽  
Exchange Interactions ◽  
Field Approximation ◽  
Molecular Field ◽  
Coupling Parameters ◽  
Structural And Magnetic Properties

The exchange interactions in PrFe11-xCoxTiCy (x=0÷2, y≤1), are analyzed on the basis of the structural and magnetic properties of polycrystalline samples. The magnetic properties of polycrystalline isomorphous compounds YFe11-xCoxTiCy have been used in order to determine the T (T=Fe+Co) sub-lattice contributions, such as the T sub-lattice mean magnetic moment and the T-T exchange interaction strength. The exchange coupling parameters JTT, JRT and the recurrent molecular field coefficients nTT, nRT have been calculated in the molecular field approximation (MCA). The effects of Co content and carbonation on the R-T (T=Fe+Co) and on the T-T exchange interactions are analyzed.

scholarly journals The effects of the thickness of magnetically hard- and soft-phase layers on magnetic properties and exchange coupling in multilayer magnets

2005 ◽  
Vol 97 (10) ◽  
pp. 10K303 ◽  
Author(s):  
W. Liu ◽  
Y. C. Sui ◽  
J. Zhou ◽  
X. K. Sun ◽  
C. L. Chen ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Exchange Coupling ◽  
Soft Phase ◽  
Phase Layers ◽  
Magnetically Hard

Effect of Wheel Speeds on the Microstructure and Magnetic Properties of Melt-Spun (Nd0.75,Dy0.25)10.5 Zr2Fe82B5.5 Ribbons

2012 ◽  
Vol 569 ◽  
pp. 23-26 ◽  
Author(s):  
Jie Qiu ◽  
Shan Dong Li ◽  
Mei Mei Liu ◽  
Jian Peng Wu ◽  
Yi Hu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Exchange Coupling ◽  
Wheel Speed ◽  
Coupling Interaction ◽  
Nanocomposite Structure ◽  
Melt Spun ◽  
Exchange Coupling Interaction ◽  
Strong Exchange ◽  
Microstructure And Magnetic Properties

Nanocomposite (Nd,Dy)2Fe14B/α-Fe magnets were prepared by directly solidification (DS). The effect of wheel speed on the magnetic properties, microstructure and exchange coupling interaction has been studied. It was found that a uniform R2Fe14B/α-Fe nanocomposite structure with fine α-Fe grains can be developed at an optimum wheel speed of about 18 m/s. Without any heat treatment, the optimal ribbons (v = 18 m/s) show a strong exchange coupling interaction and good magnetic properties, e.g. iHc=1027 kA/m, mr =0.71, (BH)max=174 kJ/m3.

scholarly journals Cluster-Assembled Iron-Platinum Nanocomposite Permanent Magnets

2006 ◽  
Vol 962 ◽  
Author(s):  
Xiangxin Rui ◽  
Zhiguang Sun ◽  
Yingfan Xu ◽  
David J. Sellmyer ◽  
Jeffrey E. Shield
Keyword(s):  
Exchange Coupling ◽  
Permanent Magnets ◽  
Volume Fraction ◽  
High Energy ◽  
Heat Treatments ◽  
Processing Route ◽  
Soft Magnetic ◽  
Soft Phase ◽  
Energy Product ◽  
Post Deposition

ABSTRACTExchange-spring nanocomposite permanent magnets have received a great deal of attention for their potential for improved the energy products. Predicted results, however, has been elusive. Optimal properties rely on a uniformly fine nanostructure. Particularly, the soft magnetic phase must be below approximately 10 nm to ensure complete exchange coupling. Inert gas condensation (IGC) is an ideal processing route to produce sub-10 nm clusters method. Two distinct nanostructures have been produced. In the first, Fe clusters were embedded in an FePt matrix by alternate deposition from two sources. Fe cluster content ranged from 0 to 30 volume percent. Post-deposition multi-step heat treatments converted the FePt from the A1 to L10 structure. An energy product of approximately 21 MGOe was achieved. Properties deteriorated rapidly at cluster concentrations above 14 volume due to uncoupled soft magnetic regions (from cluster-cluster contacts) and cooperative reversal. The second nanostructure, designed to overcome those disadvantages, involved intra-cluster structuring. Here, Fe-rich Fe-Pt clusters separated by C or SiO2 were fabricated. Phase separation into Fe3Pt and FePt and ordering was induced during post-deposition multi-step heat treatments. By confining the soft and hard phases to individual clusters, full exchange coupling was accomplished and cooperative reversal between clusters was effectively eliminated. An energy product of more than 25 MGOe was achieved, and the volume fraction of the soft phase was increased to greater than 0.5 while maintaining a coercivity of 6.5 kOe. The results provide new insight into developing high energy product nanostructured permanent magnets.

scholarly journals Exchange-Coupling Behavior in SrFe12O19/La0.7Sr0.3MnO3 Nanocomposites

Ceramics ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 100-111 ◽  
Author(s):  
Jiba Nath Dahal ◽  
Dipesh Neupane ◽  
Sanjay R. Mishra
Keyword(s):  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Exchange Coupling ◽  
Synthesis Method ◽  
Temperature Hysteresis ◽  
One Pot ◽  
Simple Method ◽  
Soft Phase ◽  
Squareness Ratio ◽  
Auto Combustion

Magnetically hard-soft (100-x) SrFe12O19–x wt % La0.7Sr0.3MnO3 nanocomposites were synthesized via a one-pot auto-combustion technique using nitrate salts followed by heat treatment in air at 950 °C. X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM) were used to characterize the structural and magnetic properties of the samples. XRD spectra revealed the formation of a mixture of ferrite and magnetite phases without any trace of secondary phases in the composite. Microstructural images show the proximity grain growth of both phases. The room temperature hysteresis loops of the samples showed the presence of exchange-coupling between the hard and soft phases of the composite. Although saturation magnetization reduced by 41%, the squareness ratio and coercivity of the nanocomposite improved significantly up to 6.6% and 81.7%, respectively, at x = 40 wt % soft phase content in the nanocomposite. The enhancement in squareness ratio and coercivity could be attributed to the effective exchange-coupling interaction, while the reduction in saturation magnetization could be explained on the basis of atomic intermixing between phases in the system. Overall, these composite particles exhibited magnetically single-phase behavior. The adopted synthesis method is low cost and rapid and results in pure crystalline nanocomposite powder. This simple method is a promising way to tailor and enhance the magnetic properties of oxide-based hard-soft magnetic nanocomposites.

NITROGENATION AND SUBSEQUENT SURFACTANT-ASSISTED HIGH ENERGY BALL MILLING OF Sm2Fe17 MELT-SPUN POWDERS

2013 ◽  
Vol 06 (04) ◽  
pp. 1350038 ◽  
Author(s):  
LIXIN ZHAO ◽  
LIYUN ZHENG ◽  
GEORGE C. HADJIPANAYIS
Keyword(s):  
Magnetic Properties ◽  
Ball Milling ◽  
High Energy ◽  
Milling Process ◽  
High Energy Ball Milling ◽  
Soft Phase ◽  
X Ray ◽  
Melt Spun ◽  
Energy Ball ◽  
Surfactant Assisted

Sm 2 Fe 17 melt-spun powders were subjected to the nitriding process and followed by surfactant-assisted high-energy ball milling (HEBM). The microstructures, morphology and magnetic properties were also investigated by X-ray diffractometer, scanning electron microscope and vibrating sample magnetometer. The results showed that the coercivities of the nitrided Sm 2 Fe 17 powders were 1.64 kOe and 3.65 kOe when the nitriding temperatures were 350°C and 450°C, respectively. When the nitriding temperature was 350°C, there was a wasp-shaped hysteresis loop, due to the soft phase of iron, formed during the nitrogenation process. The subsequent surfactant-assisted HEBM can further improve the magnetic properties of the nitrided Sm 2 Fe 17 powders and a 3 h milling process increased the coercivity of the sample nitrided at 450°C reached a high value of 6.97 kOe.

scholarly journals Synthesis of novel hard/soft ferrite composites particles with improved magnetic properties and exchange coupling

2018 ◽  
Vol 12 (3) ◽  
pp. 248-256 ◽  
Author(s):  
Faezeh Tavakolinia ◽  
Mohammad Yousefi ◽  
Seyyed Afghahi ◽  
Saeid Baghshahi ◽  
Susan Samadi
Keyword(s):  
Magnetic Properties ◽  
Exchange Coupling ◽  
Sol Gel ◽  
Phase Behaviour ◽  
Composite Particles ◽  
One Pot ◽  
Soft Phase ◽  
Auto Combustion ◽  
Physical Mixing ◽  
Soft Ferrite

SrFe12O19/Zn0.4Co0.2Ni0.4Fe2O4 hard/soft ferrite composite particles with 20, 40, 60 and 80 wt.% of soft phase were prepared by one-pot sol-gel auto-combustion and physical mixing methods. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) were used to characterize the structural and magnetic properties of the samples. XRD spectrum revealed the formation of mixed ferrite phases in the composite particles. The hysteresis loops of the samples showed the presence of exchange coupling between the hard and soft ferrites. The composite particles with 20 and 60 wt.% of the soft phase demonstrated the highest Mr/Ms ratio, i.e. 0.29 and 0.28, respectively. In addition, the highest Ms, Mr and Hc were achieved in the composite particles with 40, 60 and 20 wt.% of the soft phase, respectively. Compared to the physical mixing method (PM), the composite particles prepared by the sol-gel auto-combustion method (OP) demonstrated better magnetic properties. The exchange coupling interaction between the hard and soft ferrite phases was similar in both methods. These composite particles exhibited magnetically single phase behaviour, however, the saturation magnetization was lower in the physical mixing pared to that of the one-pot method.

scholarly journals Amorphization, Crystallization, and Magnetic Properties of Melt-Spun SmCo7−x(Cr3C2)x Alloys

2011 ◽  
Vol 2011 ◽  
pp. 1-5
Author(s):  
Liya Li ◽  
Wei Xie
Keyword(s):  
Magnetic Properties ◽  
Exchange Coupling ◽  
Melt Spinning ◽  
Amorphous State ◽  
Wheel Surface ◽  
Amorphous Phases ◽  
Annealed Ribbon ◽  
Melt Spun ◽  
Interaction Domains ◽  
Strong Exchange

Effects of Cr3C2 content and wheel surface speed on the amorphous formation ability and magnetic properties have been investigated for melt-spun SmCo7−x(Cr3C2)x (x=0.10-0.25) alloys. Ribbon melt-spun at lower wheel speed (30 m/s) has composite structure composed of mostly SmCo7, a small amount of Sm2Co17, and residual amorphous phases. The grain size of SmCo7 phase decreases with the increase of Cr3C2 content x. When melt spinning at 40 m/s, SmCo7−x(Cr3C2)x alloys can be obtained in the amorphous state for 0.15≤x≤0.25 with intrinsic coercive Hci of the order of 40–70 Oe. DSC analysis reveals that SmCo7 phase first precipitates from the amorphous matrix at 650∘C, followed by the crystallization of Sm2Co17 phase at 770∘C. Optimal coercivity Hci of 7.98 kOe and remanent magnetization Mr of 55.05 emu/g have been realized in SmCo6.8(Cr3C2)0.20 magnet subjected to melt spinning at 40 m/s and annealing at 650∘C for 5 min. The domain structure of the annealed ribbon is composed of interaction domains typically 100–400 nm in size, which indicates the presence of a strong exchange coupling between the grains.

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