Magnetic behavior of heavy rare earth RTiFe11-xCox alloys

Abstract

A series of novel alloys of the composition RTiFe11-xCox (R= Gd, Dy, Ho, Er, 0.5Er0.5Sm; 0 ≤ x ≤ 11) have been synthesized and investigated magnetically over the temperature range of 77–1100 K. The alloys exhibited the tetragonal ThMn12 structure and were almost single-phase materials for lower cobalt contents. In the range, 0 ≤ x ≤ 3, a very small amount of Fe-Co-Ti phase was present, primarily along the grain boundaries. At higher Co contents, a considerable amount of an extraneous phase of the Th2Ni17 structure was observed. The RTiFe11-xCox alloys possess saturation magnetization (σs) in the range 58–120 emu/g at 295 K. σs decreases with decreasing temperature, exhibiting an antiferromagnetic coupling of rare earth and transition metals. At 77 K, σs is in the range 39–110 emu/g. A characteristic maximum in σs is found for x ≈ 3. For the alloys we studied the easy magnetization direction appears to be axial at 295 K at both the Fe and Co ends. The Curie temperatures (Tc) of the alloys are fairly high and range from 495 K (ErTiFe11) to 1119 K (GdTiFe2Co9). In all these materials Tc is considerably enhanced by Co substitution.