Refinement of the Ferri- and Paramagnetic Phases of Magnetite from Neutron Multiple Diffraction Data

Abstract

Structural parameters for the ferrimagnetic and paramagnetic phases of magnetite have been refined from neutron multiple diffraction data. Experimental neutron multiple diffraction patterns were obtained by measuring the 111 primary reflection of a natural single crystal of this compound. Measurements were made at room temperature for the ferrimagnetic phase and at 976 K for the paramagnetic phase. The corresponding simulated patterns have been calculated byMULTI, a computer program for the simulation of neutron multiple diffraction patterns. A step-by-step process was used in the refinements according to the parameter-shift method. Both isotropic and anisotropic thermal parameters were assumed for the temperature factor. Isotropic thermal parameters were considered in two different ways: an overall parameter for all ions in the structure and three different parameters for the three special positions occupied by them in the structure. The best results were found in the refinements with anisotropic thermal parameters. In this case, the values of the profileRfactor found for these refinements were 3.00 and 3.32%, respectively, for the ferrimagnetic and paramagnetic phases.