Magnetic order of intermetallic FeGa_(3−y)Ge_y studied by μSR and~(57)Fe Moessbauer spectroscopy

摘要

Temperature-dependent magnetization, muon spin rotation, and 57Fe Moessbauer spectroscopy experimentsperformed on crystals of intermetallic FeGa_(3−y)Ge_y (y = 0.11,0.14,0.17,0.22,0.27,0.29,0.32) are reported.Whereas at y = 0.11 even a sensitive magnetic microprobe such as μSR does not detect magnetism, all othersamples display weak ferromagnetism with a magnetic moment of up to 0.22μB per Fe atom. As a function ofdoping and of temperature, a crossover from short-range to long-range magnetic order is observed, characterizedby a broadly distributed spontaneous internal field.However, y = 0.14 and 0.17 remain in the short-range-orderedstate down to the lowest investigated temperature. The transition from short-range to long-range order appearsto be accompanied by a change of the character of the spin fluctuations, which exhibit a spin-wave excitationsignature in the long-range-order part of the phase diagram. Moessbauer spectroscopy for y = 0.27 and 0.32indicates that the internal field lies in the plane perpendicular to the crystallographic c axis. The field distributionand its evolution with doping suggest that the details of the Fe magnetic moment formation and the consequentmagnetic state are determined not only by the dopant concentration, but also by the way the replacement of theGa atoms surrounding the Fe is accomplished.