Unusual ferrimagnetism in RFe₅Al₇ (R= rare earth)

The ThMn₁₂ type structure RFe₅Al₇ intermetallic compounds display a wide variety of unusual magnetic phenomena: Huge thermal and magnetic hysteresis. First observation of large negative magnetization at low temperatures when sample is cooled in magnetic field. The temperature dependence of magnetization displays one or even, in some cases, two compensation points, and a sharp maximum. Time dependent magnetization (τ {reversed tilde equals} 200 sec) is observed for DyFe₅Al₇ at 33 K and linear field dependence up to 300 kOe is observed for TbFe₅Al₇ at 4.2 K. Most features of the magnetization curves can be explained in terms of a spin structure and model previously applied to RFe₆Al₆.