Transition from the ferromagnetic state to the spin glass state in ordered Fe0.75-xAl0.25+x alloys and the temperature evolution of the magnetic structure of the Fe0.70Al0.30 alloyстатья
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Аннотация:The magnetic structure of ordered alloys Fe0.75-xAl0.25+x (x = 0, 0.025, and 0.05) is studied by Mossbauer Fe-57 spectroscopy in a temperature range of 5-295 K. An increase in the Al concentration at T = 5 K induces a transition from collinear ferromagnetism (x = 0) to a magnetic structure of the cluster-spin-glass type (x = 0.05). The unexpectedly strong effect of aluminum on the magnetic structure is explained by the anomalously high probability of formation of frustrated magnetic configurations with a large number of Al atoms in the nearest neighborhood of Fe atoms. This anomaly is associated with the establishment of a short-range order, which is a key factor determining the radical change in the magnetic structure in a narrow range of Al concentration. The "intermediate" phase of the Fe0.70Al0.30 alloy (100 K < T < 200 K) is a mixed-type magnetically ordered phase whose magnetic structure is determined by the competition of opposite exchange interactions. The nominally "ferromagnetic" phase of this alloy (T > 200 K) is characterized by strong violation of the long-range ferromagnetic order, which is due to the effect of the antiferromagnetic superexchange interaction. (c) 2005 Pleiades Publishing, Inc.