Thermal expansion property of anomalous magnetic alloy Fe70Al30

D0(3)-type Fe70Al30 shows a transition from ferromagnetism to spin glass with anomalous slow spin dynamics below 170 K. Furthermore, it shows a structural transition from D0(3) to body-centered cubic (BCC) at 823 K. In this article, the relationship between the magnetic properties, thermal expansion coefficient (TEC), and crystal structure transition of D0(3)-type Fe70Al30 is discussed. Below 170 K, TEC decreases with temperature, accompanied by a decrease in the Fe moments. In the ferromagnetic state between 170 K and the Curie temperature (T-C), TEC increases gradually with temperature. Above T-C, TEC increases rapidly. These temperature variations of TEC could be connected to the high-spin/low-spin transition and thermal spin fluctuations. During transition from D0(3) to disordered BCC at 823 K, TEC shows discontinuous behavior, similar to a first-order transformation. With further increase in temperature, TEC becomes constant. This implies that the phase transition from D0(3) to disordered BCC is accompanied by a change in spin fluctuation. (C) 2010 Elsevier B.V. All rights reserved.