Extrinsic and intrinsic magnetic properties of Co1-xFexSb3

We report magnetic properties of iron in Co1-xFexSb3 for x in the range 0 < x < 0.2, since x = 0.2 is found to be the limit of solubility of iron in the skutterudite lattice. The magnetic ions diluted in the matrix carry a small magnetic moment reduced to that of the spin-only S = 1/2 value of the Fe3+ in the low spin d(5) configuration in presence of a strong crystal field that screens the orbital momentum. The magnetic properties give evidence that a small fraction of iron is spin-frozen in magnetite ferrimagnetic clusters, and antiferromagnetic FeO clusters. Because both types of clusters represent only very minor phases, their detection by the usual analytical means such as X-rays is not possible. The remaining part is diluted in the matrix to form a semimagnetic semiconductor characterized by a Fe-Fe nearest-neighbor exchange interaction J that is antiferromagnetic, with vertical bar J vertical bar/k(B) approximate to 19.6K. (c) 2006 Elsevier B.V. All rights reserved.