Nature of magnetism of the d-subsystem in RMn2 compounds

The magnetic properties and thermal expansion of cubic Laves phases of (R, Y)Mn2 with R=Gd, La, Lu, are investigated. The stable phase at low temperatures in yttrium-rich compounds in the tetragonal distorted phase possessing an antiferromagnetic structure. In the (Gd, Y)Mn2 and (Y, Lu)Mn2 systems the cubic phase is stable at 40 and 5 atm.% of gadolinium and lutetium, respectively. It is shown that magnetic ordering of the manganese subsystem in cubic RMn2 compounds is due to f-d exchange interaction and may be interpreted in the model of initerant metamagnetism of the d-electrons. The absence of magnetic ordering of the manganese subsystem is demonstrated for the Y0.9Lu0.1Mn2 compound (with zero f-d exchange) by the neutron diffraction technique