National University of Science and Technology “MISiS”, Moscow, Russia:

V. P. Tarasov, Head of a Chair, e-mail: vptar@misis.ru
A. S. Ignatov, Asststant

Magnets, based on rare-earth transition metal system, are rapidly developed and highlighted in the permanent magnets field. As these materials provide the best magnetic performances, which are several times higher than of ferrite and injection-molded permanent magnets, the rare-earth metal-based magnets are sharply crucial for many applications and, in most cases, irreplaceable in using for cars, aircrafts, robotics, computers etc. Among other rare-earth iron intermetallics, the R₂Fe₁₇ type compound (R represents rare-earth metal) contains the largest weight percentage of iron, and thus has the highest saturation magnetic moment. It was established that Sm₂Fe₁₇N₃ compound has the Curie point increasing from 150 to 470 ^оС, as well as the saturation magnetic moment is from 0.94 up to 1.57 Tesla, and anisotropy turns to uniaxial. However, fabrication of rare-earth nitride alloys and high coercivity magnetic materials on their basis faces considerable technological problems. This paper is focused on relationship between parameters of preparation process and actual structure of high coercivity magnetic materials, and shows the optimization of the phase composition of high coercivity nanostructured magnetic materials based on rare-earth nitride alloys. Optimal phase composition of Sm₂(Fe, Co)₁₇N₃ magnetic material contains no less than 92% (wt.) of basic phase Sm₂(Fe, Co)₁₇N₃ and no more than 0.5% (wt.) of  α-Fe phase. Observed data reveal that Sm₂Fe₁₇ alloy prepared with induction melting has highly heterogeneous phase composition that is mostly determined with the cooling rate. This work demonstrates, that phase analysis allows to define the ingot areas, with the highest content of impurity phase in order to remove them from further technological processing.
This article was written within the implementation of the Agreement for subsidies No. 14.578.21.0037 of July 22, 2014. (Unique identifier of the Agreement: RFMEFI57814X0037) between National University of Science and Technology “MISiS” and the Ministry of Education and Science of Russian Federation within the realization of the Federal Target Program “Investigations and developments of priority ways of development of scientific-technological complex of Russia for 2014–2020”, approved by the Decree of the Government of Russian Federation of November 28, 2013, No. 1096.

1. Azzerboni B., Asti G., Pazetim L., Ghidini M. Magnetic Nanostructures in Modern Technology. The Netherlands : Springer, Dordrecht, 2008. 345 p.
2. Arzamasov B. N. Materialovedenie (Materials science). Moscow : N. E. Bauman Moscow State Technical University, 2004. 645 p.
3. Sun H., Coey J. M. D, Otami Y., Hurley D. P. E Magnetic properties of new series of rare-earth iron nitrides: R₂Fe₁₇N_у (у = 2, 6). Journal of Physics: Condensed Matter. 1990. Vol. 2. pp. 6465–6470.
4. Murakami R. K. Site preference and interstitial modification of (Nd, Sm)₅(Fe, Ti)₁₇. Proceedings of the 11 International Symposium on Magnetic Anisotropy and Coercivity in Rare-Earth Transition Metal Alloys. Sendai, Japan, 2000. pp. 183–190.
5. Nikitin S. A. Magnitnye svoystva redkozemelnykh metallov i ikh splavov (Magnetic properties of rare-earth metals and their alloys). Moscow : Moscow State University, 1989. 248 p.
6. Andreev A. V. Magnitnye i magnitouprugie svoystva monokristallov soedineniy R₂Fe₁₇ (Magnetic and magneto-elastic properties of monocrystals of R₂Fe₁₇ compounds). Fizika magnitnykh materialov: sbornik (Physics of magnetic materials : collection). Under the editorship of D. D. Mishin. Kalinin : State University, 1985. pp. 21–49.
7. Сou X.C. Magnetic anisotropy and magnetic phase transition in R₂Fe₁₇ with R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Ho, Er, Tm and Lu. Journal of Magnetism and Magnetic Materials. 1988. Vol. 177. pp. 1002–1007.
8. Coey J. M. D. Rare-earth iron rermanent magnets. Oxford : Clarendon Press, 1996. 178 p.
9. Tereshina I. S., Doerr M., Skourski Y., Tereshina E. A., Watanabe K., Telegina I. V., Drulis H. High-field magnetization study of R₂Fe₁₇H₃ (R = Tb, Dy, Ho and Er) single-crystalline hydrides. IEEE Transactions on Magnetics. 2011. Vol. 47, No. 10. pp. 3617–3620.
10. Tereshina I. S. Magnetoelastic effects in single-, poly-, and nanocrystalline iron- and cobalt-based rare-earth alloys and their hydrides. Russian metallurgy (Metally). 2011. No. 7. pp. 675–679.
11. Jiang W., Si. P. Z., Wang H. X., Wu Q., Liu J. J., Lee J. G., Choi C. J., Ge H. L. Structure and Magnetic Properties of Sm-Fe-N Prepared by Nitriding High Purity Sm₂Fe₁₇ Grown from Sm-rich Melt. Advanced Materials Research. 2011. Vol. 287/290. pp. 875–878.
12. Shadrov V. G., Nemtsevich L. B. Mezhkristallitnoe magnitnoe vzaimodeystvie i svoystva nanostrukturirovannykh magnitnykh materialov (Intercrystalline magnetic interaction and properties of nanostructured magnetic materials). Materialovedenie = Inorganic Materials: Applied Research. 2011. No. 6. pp. 17–22.
13. Diagrammy sostoyaniya dvoynykh metallicheskikh sistem : spravochnik (Constitution diagrams of double metallic systems : reference book). In three volumes. Chief editor: N. P. Lyakishev. Moscow : Mashinostroenie, 1997. 1024 p.