Effects of substitution of chromium and nickel on the magnetic properties of Er2Co17 and Sm2Co17

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Abstract
Ternary Er2Co17‐ and Sm2Co17‐based alloys in which Co is replaced by Ni or Cr have been studied to ascertain the effect of alloying on their magnetic properties. The systems are single phase for 0?x?7 in the case of Er2Co17−xNix and for 0?x?2 for the Cr‐substituted ternaries. Directions of magnetization, saturation magnetizations (Ms), anisotropy fields and intrinsic coercive forces (IHC) are reported for 300 and 78 K along with the measured Curie temperatures (Tc). All systems were found to be uniaxial except Er2Co13.6Ni3.4 which has planar anisotropy. Replacement of Co by Ni or Cr results in a decrease in Ms and Tc. IHC values for Er2Co17−xNix are small at room temperature but increased to ∼4 kOe at 78 K. The IHC values for Cr‐containing ternaries rise dramatically between 300 and 78 K, from ∼0 to ∼15 kOe for Er2Co15Cr2 as an example. Anisotropy fields are significantly increased by Cr substituting, reaching in the case of Sm2Co15Cr2 ∼400 kOe at 78 K. Ni is considerably less effective than Cr in enhancing HA in these ternaries. At low concentrations Ni decreases anisotropy presumably because it produces shrinkage in the c‐spacing and brings the dumbbell cobalts closer together.