Gd/sup 3+/-ESR and magnetic susceptibility of GdCu/sub 4/Al/sub 8/ and GdMn/sub 4/Al/sub 8/

摘要

Gd ESR of GdCu/sub 4/Al/sub 8/ and GdMn/sub 4/Al/sub 8/ and magnetic susceptibility of GdCu/sub 4/Al/sub 8/, GdMn/sub 4/Al/sub 8/, and YMn/sub 4/Al/sub 8/ were measured in the temperature range of 290 K-460 K and 90 K-1050 K, respectively. The occurrence of the Mn moment in YMn/sub 4/Al/sub 8/, and GdMn/sub 4/Al/sub 8/ is strongly correlated with the critical value of d/spl ap/2.6 /spl Aring/ of the Mn-Mn distance below which the Mn moment is not stable. The experimental data for GdMn/sub 4/Al/sub 8/, compared with the data for the isostructural compounds GdCu/sub 4/Al/sub 8/, and YMn/sub 4/Al/sub 8/ show that near the critical value of d, the existence of Mn moment depends not only on the value of d, but also on the local magnetic surroundings. It has been revealed that the magnetic character of Mn moment in YMn/sub 4/Al/sub 8/ and GdM/sub 4/Al/sub 8/ changes from an itinerant electron type to a local-moment type with increasing temperature.