The order of magnetic phase transition in La(Fe1-xCox)11.4Si1.6 compounds

Magnetic transitions in La(Fe1-xCox)(11.4)Si-1.6 compounds with x = 0-0.08, have been studied by DC magnetic measurements and Mossbauer spectroscopy. The temperature dependence of the Landau coefficients has been derived by fitting the magnetization, M(mu(0)H), using the Landau expansion of the magnetic free energy. For x less than or equal to 0.02 there is a strongly first-order magnetic phase transition between ferromagnetic and paramagnetic (F-P) states in zero external field and a metamagnetic transition from paramagnetic to ferromagnetic (P-F) above (c). Increasing the cobalt content drives the F-P transition towards second order and eliminates the metamagnetic transition. (C) 2003 Elsevier B.V. All rights reserved.