Magnetic phase transition in a disordered FeNi alloy: percolative scenario

The second-order magnetic phase transition in the invar Fe70Ni30 alloy was investigated. An intrinsic disorder in invar alloys leads to local variatio ns of the Curie temperature Te around its average value [T-C] As a result, large-scale inhomogeneities arise along with the usual critical fluctuation s above (Tc) Three-dimensional ND analysis allows one to obtain T-C its spr ead delta T-C and the characteristic size R-0, of the areas where T-C-varia tions occur. According to our experimental findings the "percolative" scena rio of the phase transition occurs for this alloy. (C) 2000 Elsevier Scienc e B.V. All rights reserved.