Lin-shu Kong

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

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.

A NOVEL HARD MAGNETIC MATERIAL FOR SINTERING PERMANENT-MAGNETS

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...

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

The structure and intrinsic magnetic properties of Sm 2 Fe 17-x Ga x (0≤ x≤6) compounds were studied. These compounds crystallize in the rhombohedral Th 2 Zn 17 -type structure and are single phase except for Sm 2 Fe 11 Ga 6 which contains some α-Fe. The Curie temperature T c is found first to increase and then to decrease with increasing x, attaining a maximum value of 595 K at about x=3, which is 208 K higher than that of Sm 2 Fe 17

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

Abstract The single phase compounds of R 2 Fe 17− x Ga x C 2 (R = Y, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm; x = 2 and 3) with the rhombohedral Th 2 Zn 17 -type or hexagonal Th 2 Ni 17 -type structures were prepared by arc-melting. Their formation, structure and magnetic properties were studied. The substitution of Ga in the R 2 Fe 17 C 2 results in the increase of unit cell volume and the decrease of saturation magnetization. Curie temperatures have a small change when x ≤ 2, then decreases with x The Sm 2 Fe 17− x Ga x C 2 compounds with x = 2 and 3 are found to have a uniaxial magnetocrystalline anisotropy and show a room-temperature anisotropy field of 95 and 93 kOe, respectively. Spin reorientation transitions are observed in the Er 2 Fe 17− x Ga x C 2 and Tm 2 Fe 17− x Ga x C 2 compounds. The substitution of Ga for some Fe in the R 2 Fe 17 C 2 compounds with R = Er and Tm increases the uniaxial anisotropy of the R sublattices, resulting in the increase of spin reorientation temperature.

Formation and magnetic properties of rapidly quenched R2Fe17Cx (R=Gd and Ho) compounds with higher C concentration

Abstract We have shown that the R2Fe17Cx compounds with higher carbon concentration can be prepared by melt-spinning at the quenching rates of 10–20m/s. These carbides are found to be stable at high temperatures. The introduction of carbon atoms in the R2Fe17 has a small influence on the saturation magnetization. Unit cell volumes and Curie temperatures are comparable to those of the corresponding nitrides or carbides produced by solid-gas reaction.

HIGH-COERCIVITY SM-FE-GA-C COMPOUNDS WITH TH2ZN17 STRUCTURE BY MELT-SPINNING

The magnetic hardening of the Sm2Fe14Ga3Cx was investigated by melt spinning. It was found that high coercivities can be achieved by direct quenching at the optimum substrate velocity. The coercivities of 12.6–15.0 kOe were obtained in Sm2Fe14Ga3Cx ribbons with carbon contents x from 1.0 to 2.5. The as‐quenched Sm2Fe14Ga3C1.5 ribbons had a coercivity exceeding 13 kOe within a large range of quench rates between 18 and 30 m/s. X‐ray diffraction experiments indicate that the ribbons are almost entirely comprised of the Th2Zn17 phase. It is concluded that Ga not only stabilizes the hard magnetic phase but also is very effective in raising the coercivity in the Sm2Fe14Ga3Cx melt‐spun ribbons.

THE FORMATION AND MAGNETIC-PROPERTIES OF DY2FE17CX WITH HIGH-CARBON CONTENT OBTAINED BY RAPID SOLIDIFICATION

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.

Magnetic properties of Er2Fe17Cx compounds by melt-spinning

The Er2Fe17Cx (x = 1.5, 2.0, 2.5, 2.8 and 3.0) carbides are prepared by melt-spinning. They are found to be single-phase up to x = 2.8. The as-quenched Er2Fe17Cx compounds are stable and show a structure change from hexagonal to rhombohedral with increasing carbon content. The Curie temperatures increase up to 680 K with the carbon content from x = 1.0 to 2.8. Spin reorientation transitions are observed in the as-quenched carbides.

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

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.

Structure and magnetic properties of Gd2Fe17−xGaxC2 compounds

The single‐phase compounds of Gd2Fe17−xGaxC2 (x=0, 1, 2, 3, 4, 5, and 6) with rhombohedral Th2Zn17‐type structure were prepared by melt spinning for x≤1 and arc melting for x≥2. Their formation, structure, and magnetic properties were studied. The substitution of Ga for Fe in Gd2Fe17C2 helps the formation of the 2:17‐type structure. The addition of Ga results in the increase of the lattice constants and the unit‐cell volumes. The Curie temperature has a small change when x≤2, and then decreases rapidly with increasing Ga concentration. An approximately linear decrease of the saturation magnetization with x is observed when the nonmagnetic Ga atom is substituted for Fe.