We present an investigation of the magnetic properties of the ludwigite Ni2FeO2BO3. This material is an oxyborate that presents in its crystalline structure subunits in the form of walls where the transition metal ions are located. Our Mossbauer, ac susceptibility, and magnetization measurements show that Fe and Ni ions form two independent subsystems in this material down to TN515 K. We explain this behavior in terms of a hierarchy of interactions.
Physical review. B, Condensed matter and materials physics. Woodbury. Vol. 58, no. 1 (July 1998), p. 287-292