The structure and intrinsic magnetic properties of Sm2Fe17-xGax (0 < or = x < or = 6) compounds were studied. These compounds crystallize in the rhombohedral Th2Zn17-type structure and are single phase except for Sm2Fe11Ga6 which contains some alpha -Fe. The Curie temperature Tc 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 Sm2Fe17. X-ray diffraction measurements on magnetically aligned powder samples show that samples with x < 1 and x > 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.
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.
We succeed in inserting a number of nitrogen atoms into the RTiFe11 intermetallics. The nitrides retain the ThMn12-type structure, but with an increase in the unit cell volume. The crystallographic sites located by nitrogen atoms are determined by using neutron diffraction techniques. The nitrogen atoms are found to have an effect of increasing Curie temperature and saturation magnetization. Moreover, an essential change in magnetocrystalline anisotropy is observed upon nitrogenation. By all of these effects, the NdTiFe11N1−δ compounds have excellent intrinsic magnetic properties favorable for permanent magnet applications.
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