MAGNETIC-PROPERTIES OF INTERMETALLIC COMPOUND LA0.3Y0.7MN2GE2

Intermetallic compound La0.3Y0.7Mn2Ge2 with the ThCr2Si2-type structure is antiferromagnetic (AF) below T(t)=170 K and ferromagnetic (F) between T(t) and T(C) = 340 K. Field-induced AF-F transitions are observed at temperatures below 170 K. The transition field at 4.2 K is 65 kOe on increasing field. The measurements of pressure effect on magnetic transition temperatures show that T(C) decreases and T(t) increases with pressure and the F phase disappears at pressures above 8 kbar: dT(C)/dP=-1.2 K/kbar, dT(t)/dP=19 K/kbar for P<8 kbar and dT(N)/dP=5.7 K / kbar for P > 8 kbar. The thermal expansion measurements show that the lattice constants a and c increases and decreases discontinuously, respectively. at T(t) on heating. Spontaneous magnetostriction below T(C) is positive for both a and c. The results show that the magnetic properties is sensitive to the nearest Mn-Mn distance in the c-plane.