Magnetic study of HfFe6Ge6-type solid solutions RMn6Ge6-xGax (R=Dy, Ho, Er; 0.1≤x≤1.0)

Polycrystalline DyMn(6)Gr(6-x)Ga(x) (0.1 less than or equal tox less than or equal to0.8), HoMn6Ge6-xGax and ErMn6Ge6-xGax samples (0.2 less than or equal tox less than or equal to1.0) have been studied by magnetization measurements in the temperature range 10-600 K. For increasing Ga contents, the three series display a transition from antiferromagnetic (383 less than or equal toT(N)less than or equal to 455 K) to ferrimagnetic states (377 less than or equal toT(c)less than or equal to 418 K). In the intermediate Ga concentration range, metamagnetism is observed. The critical Ga concentration upon which the compounds order ferrimagnetically increases from x = 0.4 for the Dy series to x = 0.6 and 0.8 for Ho and Er series, respectively. At low temperature, all the studied compounds display spontaneous magnetizations with more or less strong magnetocrystalline anisotropy. The coercive fields are higher in the Er compounds (H-c approximate to 20 kOe) than in the Dy and Ho ones (H-c approximate to 5 kOe). The magnetic properties are discussed and compared with those of all the other RMn6Ge6-xGax compounds (R = Sc, Y, Tb, Tm, Lu). (C) 2001 Elsevier Science B.V. All rights reserved.