Magnetism and disorder in BCC AlCuFe intermetallics

 We present here a systematic study of the structural and magnetic properties of a series of alloys around a central composition Al50Cu20Fe30, obtained by mechanical alloying. The samples have BCC crystalline structure with partial B2 order. Thermal annealing, through differential scanning calorimetry measurements, just removes some defects but does not change the crystalline structure. AC susceptibility measurements show that in spite of their structural similarity these samples have quite different magnetic behaviors. Furthermore, most of the samples show a complex magnetic evolution with temperature. Some samples have a cluster glass-like behavior at low temperatures and a superparamagnetic-like one at higher temperatures. A model of magnetic clusters originating in composition fluctuations across the alloy is proposed to explain the observed magnetic properties.