Thermal expansion anomaly and spontaneous magnetostriction of Gd 2Fe 17 compound

Abstract

Materials with negative thermal expansion have many practical applications. However, these materials are known in only several oxide systems, and when the negative thermal expansion occurs, the contraction is usually small and limited to a narrow temperature range beyond room temperature. For obtaining a compound with negative thermal expansion in broad temperature range, the structural and magnetic properties of Gd 2Fe 17 compound were investigated by means of X-ray diffraction and magnetization measurements. The Gd 2Fe 17 compound annealed at 1050 °C had a Th 2Zn 17-type structure. There existed an anisotropic strong spontaneous magnetostriction and a negative thermal expansion in Gd 2Fe 17 compound. The average thermal expansion coefficients was ▪=−7.40×10 −6/K in the temperature range of 294–453 K and ▪=−1.80×10 −5/K in 453–534 K, respectively. The spontaneous magnetostrictive deformation ω S decreased from 4.34×10 −3 to near zero with temperature increasing from 294 to 572 K. The spontaneous linear deformation λ c was much larger than λ a at the same temperature below about 500 K.