A novel hard magnetic compound series with composition Sm2Fe14Ga3Cx (x=0, 0.5, 1.0, 1.5, 2.0, and 2.5) was prepared by arc melting. The carbides crystallize in the rhombohedral Th2Zn17‐type structure and are single phase except for Sm2Fe14Ga3 and Sm2Fe14Ga3C0.5 which contain some amounts of α‐Fe. The substitution of Ga is found to play an important role in the stability of high carbon rare‐earth iron compounds with 2:17‐type structure. The Curie temperatures of Sm2Fe14Ga3Cx are 200–240 K higher than that of Sm2Fe17. All compounds with x=0–2.5 exhibit an easy c‐axis anisotropy at room temperature. The anisotropy fields increase with increasing carbon concentration from 70 kOe for x=0 to at least 90 kOe for x≥1.5. A room‐temperature coercivity of 15 kOe is obtained in Sm2Fe14Ga3C1.5 prepared by melt spinning at a speed of 30 m/s.

Structure and magnetic properties of Sm2Fe14Ga3Cx (x=0–2.5) compounds prepared by arc melting

We have discovered that the substitution of Ga or Si for Fe in Sm2Fe17Cx helps the formation of high‐carbon rare‐earth iron compounds with 2:17‐type structure. We have succeeded in preparing Sm2Fe15M2Cx (M=Ga, x=0, 1.0, 2.0, and 3.0; M=Si, x=0, 0.5, 1.0, and 1.5) compounds with Th2Zn17‐type structure by arc melting. The carbides are single phase except for Sm2Fe15Ga2C3.0, which contains a few percent of α‐Fe. The Curie temperature TC of Sm2Fe15Si2Cx compounds is found to increase from 550 to 590 K, as x increases from 0 to 1.5. For Sm2Fe15Ga2Cx, TC increases with x from 565 K for x=0 to 635 K for x=2.0, and then decreases with x. Room‐temperature saturation magnetization of these carbides is in excess of 100 emu/g and has a small dependence on carbon content. All compounds of Sm2Fe15M2Cx studied in this work except for Sm2Fe15Si2 exhibit an easy c‐axis anisotropy at room temperature and show an anisotropy field of higher than 90 kOe for x≥1.0. The present work suggests the possibility of producing high‐pe...

A novel hard magnetic material for sintering permanent magnets

Chapter 4 Magnetism and processing of permanent magnet materials

A comprehensive review is given of recent advances in the study of metastable phases in rare-earth permanent magnets. The relations between the structures of the metastable and equilibrium phases and the transformations from the former to the latter are discussed. The formation of the phases is found to depend on the difference between the symmetries of the metastable and equilibrium phases. The magnetic properties of the metastable-phase rare-earth permanent magnets synthesized by various processes, such as mechanical alloying, mechanical milling, rapid quenching, hydrogenation, disproportionation, desorption and recombination, solid-state reaction, solid-gas reaction, self-flux and sputtering, are compared. The main conclusion of this article is that searching for new metastable phases with high magnetic performance will be one of the most active directions in the research on rare-earth permanent magnets.

http://iopscience.iop.org/article/10.1088/0022-3727/33/22/201/pdf

Metastable phases in rare-earth permanent-magnet materials

Rare-earth iron-based intermetallic compounds and their carbides: Structure and magnetic behaviors

The structure and intrinsic magnetic properties of Sm2Fe17-xGax (0 5 exhibit easy-plane anisotropy while samples with 1 < x < 5 exhibit easy c-axis anisotropy. The samples with x = 1 and 5 show a mixture of easy-plane and easy-axis behaviour.

Magnetic anisotropy of Sm2Fe17-xGax compounds with 0 < or = x < or = 6

Formation and magnetic-properties of rapidly quenched r2fe17cx (r=gd and ho) compounds with higher-c concentration

Formation and magnetic properties of R2Fe17−xGaxC2 compounds prepared by arc-melting

The carbides Dy2Fe17Cx with x=1.5-3.0 have been successfully prepared by the melt-spinning method. The X-ray diffraction patterns and the thermomagnetic curves show that they are of single phase in general with Th2Zn17 structure type when x=1.5, 2.0, 2.5 and 2.8 with a small amount of alpha -Fe as an impurity phase, while for x=3.0 the proportion of the alpha -Fe phase is high. The lattice parameters a and c are both enlarged and increase with the carbon content x. The Curie temperatures Tc are greatly enhanced when x<2.5 and remain almost constant when x=2.5-3.0, but the saturation magnetizations, sigma s, increase slightly. The Dy2Fe17Cx ribbons still maintain the rhombohedral Th2Zn17-type structure after being annealed at 1100 degrees C for 14 h, which indicates the high stability of Dy2Fe17Cx (x=1.5-3.0) compounds obtained by rapid solidification. The heat-treated ribbon samples can be magnetically oriented and prefer an easy-plane anisotropy at room temperature.

http://iopscience.iop.org/article/10.1088/0953-8984/4/40/003/pdf

The formation and magnetic properties of Dy2Fe17Cx with high carbon content obtained by rapid solidification

The authors have successfully prepared the carbides R2Fe17Cx (R identical to Y, Gd, Tb, Dy, Ho and Er) with a high carbon content x=1.5 and 2.0 by the melt-spinning method. The carbides have a single rhombohedral Th2Zn17 structure phase and are highly stable to at least 1100 degrees C. The Curie temperatures TC are raised enormously and the saturation magnetizations change little upon carbonation. The average enhancements of TC are about 220 K for R2Fe17C1.5 and 265 K for R2Fe17C2.0. The volume dependence of the exchange interaction has been discussed. The Curie temperatures are analysed in terms of a mean-field model. The spin reorientation is observed to be 133 K for Er2Fe17C1.5 and 141 K for Er2Fe17C2.0.

https://iopscience.iop.org/article/10.1088/0953-8984/5/13/015/pdf

Lin-shu Kong

Papers

Magnetic anisotropy of Sm2Fe17-xGax compounds with 0 < or = x < or = 6

Formation and magnetic-properties of rapidly quenched r2fe17cx (r=gd and ho) compounds with higher-c concentration

Formation and magnetic properties of R2Fe17−xGaxC2 compounds prepared by arc-melting

The formation and magnetic properties of Dy2Fe17Cx with high carbon content obtained by rapid solidification

The crystal structure and magnetic properties of R2Fe17Cx (x=1.5 and 2.0) prepared by the melt-spinning method