Magnetic Ordering In Erfe0.3ge2 And Erni0.65ge2 Compounds

The magnetic ordering in ErFe0.3Ge2 and ErNi0.65Ge2 compounds crystallizing in the orthorhombic structure of the CeNiSi2-type has been investigated by neutron diffraction and magnetic measurements. The Er magnetic moments have been found to order antiferromagnetically below 2.5 K in ErFe0.3Ge2 and 2.3 K in ErNi0.65Ge2. The magnetic structure of the former compound can be described by the propagation vector k = (0.044(1), 0, 0.384(1)). The Er magnetic moments are aligned along the a-axis and alternate with the sequence ++-- in the unit cell. At 1.5 K they are equal to 5.9(1) mu(B). In contrast, the magnetic unit cell of ErNi0.65Ge2 has been established to be equal to the chemical one. The magnetic moments in this compound are arranged in a collinear manner pointing along the a-axis with the sequence +-+-. The Er moment value measured at 1.5 K is 2.90(8) mu(B).