A number of new ternary ferromagnetic compounds have been prepared1 which have the general formula A1 4MnX1 1 (A=Ca, Sr and X=As, Sb, or Bi) and are isostructural to the main group Zintl compounds Ca1 4GaAs1 1 (Ref. 2) and Ca1 4AlSb1 1.3 The Mn-Mn nearest-neighbor distances in these compounds are ≥11 Å. Each of the compounds containing Mn is a metallic ferromagnet with a Curie transition in the neighborhood of 40–60 K. From magnetization measurements in the paramagnetic regime it appears that the Mn has a valence of +3 and that there are good local moments associated with the four unpaired electrons. This is in contrast to the low-temperature state in which the ordered ferromagnetic moment is only about 2.5 μB/Mn. Since no structural change is found upon cooling the sample below the Curie temperature and resistivity measurements show a strong interaction between the conduction electrons and the local moments, we suggest that the ferromagnetic moment is reduced by coupling with the conduction electrons.
ASJC Scopus subject areas
- Physics and Astronomy(all)