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

EXCHANGE–COUPLING INTERACTION AND EFFECTIVE ANISOTROPY OF Nd2Fe14B/a-Fe/Nd2Fe14B SANDWICH MULTILAYERED THIN FILM

2010 ◽  
Vol 24 (29) ◽  
pp. 5815-5820
Author(s):  
YAN SUN
Keyword(s):  
Thin Film ◽  
Exchange Coupling ◽  
Hard Phase ◽  
Soft Phase ◽  
Effective Anisotropy ◽  
Coupling Interaction ◽  
Multilayered Thin Film ◽  
Phase Layers ◽  
Exchange Coupling Interaction ◽  
The Given

The exchange–coupling interaction between soft and hard phase layers and the effective anisotropy K eff have been investigated by putting forward an expression of anisotropy at grain interface, [Formula: see text], which is suitable for different coupling conditions in multilayered thin film. The results showed when the dimensions of soft and hard phases are the same (described by b), K eff increases first, then decreases, and reaches a maximum at a certain value of b with increasing b. For the given hard phase dimension bh, K eff decreases monotonously with increasing soft phase dimension bs. However, for the given bs, K eff increases monotonously with the increase of bh. When the dimensions of soft and hard phases are the same, the variation of K eff in multilayered thin film is very similar to that of coercivity given by Yang et al. Our results explained the experimental phenomenon better.

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.

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.

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.

Suitable Nanostructures for Obtaining the Maximum Energy Product in Magnets

2016 ◽  
Vol 869 ◽  
pp. 614-619 ◽  
Author(s):  
Marcos Flavio de Campos ◽  
Sergio Antonio Romero
Keyword(s):  
Exchange Coupling ◽  
Maximum Energy ◽  
Paramagnetic Phase ◽  
Soft Phase ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Magnetostatic Coupling ◽  
Relevant Role ◽  
Magnetically Hard ◽  
Two Phases

The existence of exchange coupling or magnetostatic coupling between two phases, one magnetically hard and other magnetically soft is a way for obtaining higher maximum energy product (BHmax). In this study, it is discussed the microstructures for obtaining either exchange coupling or magnetostatic coupling in real materials. One relevant condition is that the assumptions of the Stoner-Wohlfarth model should be obeyed, with both phases, hard and soft, with dimensions less than single domain particle size. A real possibility is enveloping a spherical grain of hard phase with a first shell of soft phase, and another second shell or layer of a paramagnetic phase. The paramagnetic phase may play relevant role promoting magnetically decoupling between the grains.

Rare earth permanent magnetic nanostructures: chemical design and microstructure control to optimize magnetic properties

2021 ◽  
Author(s):  
Junjie Xu ◽  
Kai Zhu ◽  
Song Gao ◽  
Yanglong Hou
Keyword(s):  
Magnetic Properties ◽  
Rare Earth ◽  
Exchange Coupling ◽  
Magnetic Nanostructures ◽  
Microstructure Control ◽  
Size And Shape ◽  
Chemical Design

The routes for the optimization of the magnetic properties of rare earth permanent magnetic nanostructures are discussed, i.e. the control of microstructure, such as size and shape as well as the exchange-coupling interactions.

scholarly journals Microstructure and magnetic properties of Nd-Fe-B-(Re, Ti) alloys

Nukleonika ◽  
2015 ◽  
Vol 60 (1) ◽  
pp. 29-33
Author(s):  
Mariusz Hasiak
Keyword(s):  
Magnetic Properties ◽  
Phase Composition ◽  
Volume Fraction ◽  
Magnetic Characteristics ◽  
Ti Alloys ◽  
Wide Range ◽  
Magnetically Hard ◽  
Ti Addition ◽  
Microstructure And Magnetic Properties

Abstract The microstructure and magnetic properties of nanocomposite hard magnetic Nd-Fe-B-(Re, Ti) materials with different Nd and Fe contents are studied. The role of Re and Ti addition in phase composition and volume fraction of the Nd-Fe-B phase is determined. All samples are annealed at the same temperature of 993 K for 10 min. Mössbauer spectroscopy shows that the addition of 4 at.% of Re to the Nd8Fe78B14 alloy leads to creation of an ineligible amount of the magnetically hard Nd2Fe14B phase. Moreover, the microstructure and magnetic characteristics recorded in a wide range of temperatures for the Nd8Fe79−xB13Mx (x = 4; M = Re or Ti) alloys are also analyzed.

A Study on The Phase Transformation and Exchange-Coupling of (Nd0 95La0 05)9 5FebalCo5Nb2B10.5 Nanocomposites

1999 ◽  
Vol 577 ◽  
Author(s):  
Q. Chen ◽  
B. M. Ma ◽  
B. Lu ◽  
M. Q. Huang ◽  
D. E. Laughlin
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Phase Transformation ◽  
Thermal Treatment ◽  
Grain Growth ◽  
Exchange Coupling ◽  
Phase Distribution ◽  
Maximum Energy ◽  
Treatment Temperature ◽  
Phase Identification

ABSTRACTThe phase transformation and the exchange coupling in (Ndo095Lao005)9.5FebaICOsNb 2BI05 have been investigated. Nanocomposites were obtained by treating amorphous precursors at temperatures ranging from 650TC to 9500C for 10 minutes. The magnetic properties were characterized via the vibrating sample magnetometer (VSM). X-ray diffraction (XRD), thermomagnetic analysis (TMA), and transmission electron microscopy (TEM) were used to perform phase identification, measure grain size, and analyze phase distribution. The strength of the exchange coupling between the magnetically hard and soft phases in the corresponding nanocomposite was analyzed via the AM-versus-H plot. It was found that the remanence (Br), coercivity (Hci), and maximum energy product (BHmax) obtained were affected by the magnetic phases present as well as the grain size of constituent phases and their distribution. The optimal magnetic performance, BHm, occurred between 700°C to 750°C, where the crystallization has completed without excessive grain growth. TMA and TEM indicated that the system was composed of three phases at this point, Nd2(Fe Co) 14B, ca-Fe, and Fe3B. The exchange coupling interaction among these phases was consistently described via the AM-versus-H plot up to 750°C. The Br, Hci, and BHmax degraded severely when the thermal treatment temperature increased from 750°C. This degradation may be attributed to the grain growth of the main phases, from 45 to 68nm, and the development of precipitates, which grew from 5nm at 750°C to 12nm at 850°C. Moreover, the amount of the precipitates was found to increase with the thermal treatment temperatures. The precipitates, presumably borides, may cause a decrease in the amount of the a-Fe and Fe 3B and result in a redistribution of the Co in the nanocomposites. The increase of the Co content in the Nd 2(Fe Co) 14B may explain the increase of its Curie temperature with the thermal treatment temperatures. In this paper, we examine the impacts of these factors on the magnetic properties of (Ndo 95Lao 05)9 5FebaICosNb2B10.5 nanocomposite.

scholarly journals Design of Pure Heterodinuclear Lanthanoid Cryptate Complexes

2021 ◽  
Author(s):  
Christian Dirk Buch ◽  
Steen Hansen ◽  
Dmitri Mitcov ◽  
Camilla Mia Tram ◽  
Gary Nichol ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Magnetic Properties ◽  
13C Nmr ◽  
Exchange Coupling ◽  
Lanthanide Ions ◽  
Squid Magnetometry ◽  
Counter Ion ◽  
Synthetic Procedure ◽  
Optical And Magnetic Properties ◽  
Fine Tune

Heterolanthanide complexes are difficult to synthesize owing to the similar chemistry of the lanthanide ions. Conse-quently, very few purely heterolanthanide complexes have been synthesized. This is despite the fact that such complexes hold inter-esting optical and magnetic properties. To fine-tune these properties, it is important that one can choose complexes with any given combination of lanthanides. Herein we report a synthetic procedure which yields pure heterodinuclear lanthanide cryptates LnLn*LX3 (X = NO3- or OTf-) based on the cryptand H3L = N[(CH2)2N=CH-R-CH=N-(CH2)2]3N (R = m-C6H2OH-2-Me-5). In the synthesis the choice of counter ion and solvent prove crucial in controlling the Ln-Ln*composition. Choosing the optimal solvent and counter ion affords pure heterodinuclear complexes with any given combination of Gd(III)-Lu(III) including Y(III). To demon-strate the versatility of the synthesis all dinuclear combinations of Y(III), Gd(III), Yb(III) and Lu(III) were synthesized resulting in 10 novel complexes of the form LnLn*L(OTf)3 with LnLn* = YbGd 1, YbY 2, YbLu 3, YbYb 4, LuGd 5, LuY 6, LuLu 7, YGd 8, YY 9 and GdGd 10. Through the use of 1H, 13C NMR and mass spectrometry the heterodinuclear nature of YbGd, YbY, YbLu, LuGd, LuY and YGd was confirmed. Crystal structures of LnLn*L(NO3)3 reveal short Ln-Ln distances of ~3.5 Å. Using SQUID magnetometry the exchange coupling between the lanthanide ions was found to be anti-ferromagnetic for GdGd and YbYb while ferromagnetic for YbGd.

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