Magnetism influenced by structural disorder in melt-spun DyMn_(6-x)Ge_(6-x)Fe_xAl_x (x = 2.5, 3)

摘要

Different chemical and/or geometrical orders were found in melt-spun DyMn_(6-x)Ge_(6-x)Fe_xAl_x with x = 2.5 and 3 having fully amorphous and mixed (crystalline and amorphous) structure, respectively. Thermal variations in magnetization M from liquid helium up to room temperature for both samples are similar. Magnetization value at zero field cooled curve reaches about 0.1 μ_B per formula unit at 2 K and then increases. Two maxima are visible, the first at 50 K (a sharp effect) and the second very broad ranging from 150 to 200 K. ~(57)Fe Moessbauer spectrometry investigation revealed a remaining magnetic component in addition to a prevailing quadrupolar feature. Application of a weak external magnetic field causes an increase in the mean hyperfine magnetic field B_(hyp) and the volume fraction of magnetic component. This observation was confirmed by results of M(T), M(H) and AC magnetic susceptibility measurements. In short-range ordered crystallographic zones characteristic of melt-spun DyMn_(6-x)Ge_(6-x)Fe_xAl_x (x = 2.5,3) alloys, the related magnetic ordering, called the mictomagnetism or the cluster spin glass appears.