ANTIFERROMAGNETIC PROPERTIES IN RFE2GE2 (R=TB,DY,HO)

X-ray and neutron diffraction measurements confirm that RFe2Ge2 (R = T b, Dy and Ho) compounds show the tetragonal ThCr2Si2 type of crystal s tructure. Magnetization and magnetic susceptibility data indicate anti ferromagnetic behaviour below the Neel temperatures at 8.5 K in TbFe2G e2 and 3.35 K in DyFe2Ge2. A metamagnetic transition at H-c = 11 kOe a nd T = 4.2 K has been detected in TbFe2Ge2. The other two compounds gi ve at 4.2 K magnetization curves characteristic for paramagnetic mater ials up to H = 50 kOe. The magnitudes of magnetic moments at H = 50 kO e are smaller than the free ion values for all three compounds. TbFe2G e2 and DyFe2Ge2 exhibit at 1.5 K modulated antiferromagnetic order des cribed by two component wavevectors k = \k(x), O, k(z)\. The magnetic moments are localized on the lanthanide ions and amount at 1.5 K to 7. 68(11) and 7.3(3) mu(B) in TbFe2Ge2 and DyFe2Ge2 respectively. Diffuse magnetic peaks observed at 1.5 K in the neutron diffraction pattern o f HoFe2Ge2 indicate that a long-range antiferromagnetic order starts t o set up at this temperature.