Magnetic order of intermetallic FeGa$_{3-y}$Ge$_y$ studied by $\mu$SR and $^{57}$Fe M'ossbauer spectroscopy

摘要

Temperature dependent magnetization, muon spin rotation and $^{57}$FeM\"ossbauer spectroscopy experiments performed on crystals of intermetallicFeGa$_{3-y}$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 $\mu$SR doesnot detect magnetism, all other samples display weak ferromagnetism with amagnetic moment of up to 0.22 $\mu_B$ per Fe atom. As a function of doping andof temperature a crossover from short range to long range magnetic order isobserved, characterized by a broadly distributed spontaneous internal field.However, the $y=0.14$ and $y=0.17$ remain in the short range ordered state downto the lowest investigated temperature. The transition from short range to longrange order appears to be accompanied by a change of the character of the spinfluctuations, which exhibit spin wave excitations signature in the LRO part ofthe phase diagram. M\"ossbauer spectroscopy for $y=0.27$ and 0.32 indicatesthat the internal field lies in the plane perpendicular to the crystallographic$c$ axis. The field distribution and its evolution with doping suggest that thedetails of the Fe magnetic moment formation and the consequent magnetic stateare determined not only by the dopant concentration but also by the way thereplacement of the Ga atoms surrounding the Fe is accomplished.