Magnetic hysteresis in the Cu-Al-Mn intermetallic alloy: Experiments and modeling

We study isothermal magnetization processes in the Cu-Al-Mn intermetallic a lloy. Hysteresis is observed at temperatures below the spin-freezing of the system. The characteristics of the hysteresis cycles as a function of temp erature and Mn content (magnetic element) are obtained. At low temperature (less than or similar to 5 K) a change from smooth to sharp cycles is obser ved with increasing Mn content, which is related to the decrease of configu rational disorder. We also study a zero-temperature site-diluted Ising mode l, suitable for the description of this Cu-Al-Mn system. The model reproduc es the main features of the hysteresis loops observed experimentally. It ex hibits a disorder-induced critical line separating a disordered phase from an incipient ferromagnetic ground state. The comparison between the model a nd the experiments allows us to conclude that the observed change in the ex perimental hysteresis loops can be understood within the framework of the t heory of disorder-induced criticality in fluctuationless first-order phase transitions. [S0163-1829(99)13821-9].