7.9.3 Saturation magnetization and Curie temperature

Reported here are the results of experiments carried out to demonstrate the magnetic performance of dysprosium (Dy) to enhance the capability of undulators. Tiny pieces of monocrystalline Dy surrounded by permanent magnets (PMs) work as pole pieces (PPs) to concentrate the magnetic flux, when cooled down below the Curie temperature of 85 K. A PP made of Dy is much more attractive than one made of a conventional material, because its saturation magnetization is much higher. Furthermore, it also allows for a more flexible selection of PM material, potentially leading to further enhancement of the performance of short-period undulators. Besides these advantages, practical issues related to using Dy PPs and countermeasures against them are discussed.

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Nanocrystalline MnFe2O4 produced by niobium doping

Journal of Materials Research ◽

10.1557/jmr.1999.0535 ◽

1999 ◽

Vol 14 (10) ◽

pp. 3957-3961 ◽

Cited By ~ 12

Author(s):

T. K. Kundu ◽

D. Chakravorty

Keyword(s):

Curie Temperature ◽

Saturation Magnetization ◽

Active Oxygen ◽

Niobium Doping ◽

Ferrimagnetic Phase ◽

Break Up

Nanosized MnFe2O4 phase with diameters in the range 13.7 to 100 nm were produced by calcination and sintering treatments in the system zNb2O5 · (50 – z)MnO · 50Fe2O3 with z having values between 0 and 20. Nb5+ ions are believed to give rise to vacancies in the Mn2+ sites, which break up the coupling of ferrimagnetically active oxygen polyhedra. The Curie temperature decreases as the size of the MnFe2O4 phase is reduced. This is explained on the basis of a decrease in the number of exchange pairs of the type Mn2+–Fe3+. The coercivity increases with a decrease in the size of the ferrimagnetic phase. This is believed to arise due to a decrease in saturation magnetization as the size of the MnFeO4 phase is reduced.

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Effect of Ball Milling on Magnetic Properties of Nb Substituted R2Fe16Nb1 (R: Gd and Er) Alloys

MRS Proceedings ◽

10.1557/opl.2013.392 ◽

2013 ◽

Vol 1516 ◽

pp. 227-231

Author(s):

B. K. Rai ◽

S. R. Mishra ◽

S. Khanra ◽

K. Ghosh

Keyword(s):

Magnetic Properties ◽

Curie Temperature ◽

Saturation Magnetization ◽

Ball Milling ◽

Grain Refinement ◽

High Energy ◽

High Energy Ball Milling ◽

Lattice Expansion ◽

Energy Ball

AbstractIn this work, we report the effect of high energy ball milling (HEBM) on Nb doped R2Fe16Nb1 (R= Gd, Er) compounds. The focus of the work is to bring enhancement in magnetic properties of R2Fe17 (2:17) compounds with the ball milling. Specifically, we find that the ball milling increases saturation magnetization, coercivity, and Curie temperature. The increase in the magnetization and Curie temperature upon ball milling is related to the lattice expansion and microstrains while the increase in coercivity is related to the grain refinement.

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