GD3-ESR AND MAGNETIC-SUSCEPTIBILITY OF GDCU4AL8 AND GDMN4AL8()

Gd ESR of GdCu4Als and GdNn4Als and magnetic susceptibility of GdCu4Al 8, GdMn4Al8, and YMn4Al8 were measured in the temperature range of 290 1-460K and 901-1050K, respectively. The occurrence of the Mn moment in YMn4Al8 and GdMn4Al8 is strongly correlated with the critical value o f d almost-equal-to 2.6 angstrom of the Mn-Mn distance below which the Mn moment is not stable. The experimental data for GdMn4Al8, compared with the data for the isostructural compounds GdCu4Al8 and YMn4Al8, s how that near the critical value of d, the existence of Mn moment depe nds not only on the value of d, but also on the local magnetic surroun dings. It has been revealed that the magnetic character of Mn moment i n YMn4Al8 and GdMn4Al8 changes from an itinerant electron type to a lo cal-moment type with increasing temperature.