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

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. [ABSTRACT FROM AUTHOR]