MAGNETIC-PROPERTIES OF YMNXAL12-X (X=4, 5, 6)

Magnetic susceptibility of YMnxAl12-x (x=4, 5, 6) with TbMn12 structur e was measured at temperatures 90K to 900K. These compounds show varie d magnetic behaviors depending upon the relative abundance of Mn atoms in the 8f, 8j, and 8i crystallographic sites. In the high temperature range, the temperature dependence of the susceptibility is of the Cur ie-Weiss type. The occurrence of a Mn moment in YMn4Al8 and YMn8Al6 is strongly correlated with the critical value d almost-equal-to 2. 6 an gstrom of Mn-Mn distance below which the Mn moment collapses. In YMn8A l6 both the magnetic and the nonmagnetic Mn atoms were observed to coe xist. It has been revealed that the magnetic character of Mn moment in the 8f sites of these two compounds changes from an itinerant electro n type to a local moment type with increasing temperature. A transitio n to a spin glass state at low temperatures for YMn5Al7 was suggested.