MAGNETIC AND MAGNETOOPTICAL PROPERTIES OF MN5(GE1-XMX)3 ALLOYS WITH M=SN, PB

We report on the magnetic and magneto-optical properties of the interm etallic alloys Mn5(Ge1-xMx)3, where M=Sn, Pb. Generally, these alloys were ordered ferromagnetically at T greater-than-or-equal-to 300 K for x<0.3. The structure of Mn5(Ge1-xSnx)3 remains in the hexagonal Mn5Si 3(hP16) phase up to x=0.25 and then changes to Ni2In (hP6) as x approa ches 1. The magnetization and Curie temperature of these alloys is lar gest for small x and reach a minimum value near x = 0. 5. The room tem perature Polar Kerr rotation, however, increases from -0.06-degrees at x = 0 to maximum value of -0.12-degrees at x=0.1 before decreasing to ward zero for x>0.3. The Mn5(Ge1-xPbx)3 samples show a Mn5Si3 structur e with ferromagnetic behavior for x less-than-or-equal-to 0.3, and var ying structure with rapidly decreasing magnetization above x = 0. 3. T he magnetic behavior observed was complex for x greater-than-or-equal- to 0. 3. The Kerr rotation of the Pb-doped alloys in the ferromagnetic region monotonically decreases from -0.06-degrees to zero at x almost -equal-to 0.3.