Magnetic properties of disordered interacting electron system FeAl2-xGax (0 ≤ x ≤ 0.5): Origin of local moment behaviour and the stabilization of an antiferromagnetic phase by weak interplanar magnetic interaction

Abstract In this report, we have investigated the magnetic properties of the disordered interacting electron system FeAl 2- x Ga x (0 ≤  x  ≤ 0.5) through the measurements of dc magnetization, ac susceptibility and heat capacity, and constructed the magnetic phase diagram. This system shows an intriguing phenomenon in which an antiferromagnetic transition occurs concomitantly with a disorder-induced weak localization of electrons implying a cooperative nature of the disorder-induced effects and electron-electron interactions which is in contradiction to their established competitive nature. Our investigation reveals that, in addition to the antiferromagnetic transition at T N , a spin glass transition occurs at a lower temperature at T g ( T g N ). As the Ga concentration increases, T N increases while T g decreases. The investigation reveals that the Fe-Fe antiferromagnetic interactions predominantly lie in a plane and the antiferromagnetic phase is stabilized by a weak interplanar Fe-Fe interaction. With increasing Ga concentration, this interplanar Fe-Fe distance decreases and results in the increase of the Neel temperature T N . Fe moments in this system are found to be partially localized due to the interplay between disorder and electron-electron interactions. Competing interactions between the finite spin clusters give rise to a cluster spin glass state at low temperatures.