The interplay between the lattice and magnetism in La(Fe11.4Al1.6)C0.02 studied by powder neutron diffraction

Abstract

The crystallographic structure and magnetic properties of La(Fe11.4Al1.6)C0.02 are studied by magnetic measurement and powder neutron diffraction with temperature and applied magnetic field. Rietveld refinement shows that La(Fe11.4Al1.6)C0.02 crystallizes into the cubic NaZn13-type with two different Fe sites: FeI (8b) and FeII (96i), and that Al atoms preferentially occupy the FeII site. A ferromagnetic state can be induced at a medial temperature of 39 K-139 K by an external magnetic field of 0.7 T, and a large lattice is correspondingly found at 100 K and 0.7 T. In all other conditions, La(Fe11.4Al1.6)C0.02 has no net magnetization in the paramagnetic (T > TN = 182 K) or antiferromagnetic states, and thus keeps its small lattice. Analysis of the Fe—Fe bond length indicates that the ferromagnetic state prefers longer Fe—Fe distances.