Thermal expansion anomaly and magnetic properties of Nd₂AlFe_16−xMn_x compounds

¹ Department of Physics, Tianjin Normal University, Tianjin, 300074, P.R. China
² Department of Physics, Shandong University, Jinan, 250100, P.R. China

Corresponding author: yanminghao@eyou.com

Received: 10 May 2005
Revised: 13 September 2005
Accepted: 25 October 2005
Published online: 8 February 2006

Abstract

The structural and magnetic properties of Nd₂AlFe_16−xMn_x (x = 1, 2, 3, 4, and 5) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The Nd₂AlFe_16−xMn_x compounds have a rhomhedral Th₂Zn₁₇-type structure. There exist an anisotropic strong spontaneous magnetostriction in magnetic state and a negative thermal expansion near their Curie temperatures. The nearly zero thermal expansion coefficient is found over a broad temperature range including room temperature from 103 to 342 K for Nd₂AlFe₁₅Mn compound. In the magnetic state, the thermal expansion coefficients of Nd₂AlFe_16−xMn_x compounds increase with the increasing Mn concentrations x. Mn concentration dependences of the lattice parameters and unit-cell volume, the spontaneous magnetostrictive deformation, the Curie temperature, and the saturation magnetization have been discussed.