Magnetic and transport properties of RCr0.3Ge2 (R=Tb, Dy, Ho and Er) compounds

The magnetic and transport properties of ternary rare-earth chromium germanides RCr0.3Ge2 (R=Y and Tb–Er) have been determined. X-ray and neutron diffraction studies indicate that these compounds have the CeNiSi2-type structure (space group Cmcm) [1]. Magnetic measurements reveal the antiferromagnetic ordering below TN equal to 18.5 K (R=Tb), 11.8 K (Dy), 5.8 K (Ho) and 3.4 K (Er). From the neutron diffraction data the magnetic structures have been determined. For TbCr0.3Ge2 and DyCr0.3Ge2 at low temperatures the magnetic ordering can be described by two vectors k1=(12,0,0) and k2=(14,0,14), and k1′=(12,0,0) and k2′=(12,0,12), respectively. In HoCr0.3Ge2 and ErCr0.3Ge2 the ordering can be described by one propagation vector equal to (12,12,0) and (0,0,0.4187(2)), respectively. In DyCr0.3Ge2 some change in the magnetic ordering is observed at Tt=5.1 K. In temperature range from Tt to TN the magnetic ordering is given by one propagation vector k=(12,0,0). YCr0.3Ge2 is a Pauli paramagnet down to 1.72 K which suggests that in the entire RCr0.3Ge2 series the Cr atoms do not carry magnetic moments. All compounds studied exhibit metallic character of the electrical conductivity. The temperature dependencies of the lattice parameters reveal strong magnetostriction effect at the respective Nèel temperatures.

In the neutron diffraction pattern of TbCr0.3Ge2 compound collected at 1.5 K the additional peaks of magnetic origin form two groups. The first one, with strong intensities, can be indexed by the propagation vector k=(12,0,0) (a), while the second one, with small intensities, can be described by the propagation vector k=(14,0,14) (b). The analysis of the magnetic peak intensities indicates that the Tb magnetic moments located at the positions Tb1 (0,y  ,14), Tb2 (0,−y  ,34), Tb3 (12,12+y  ,14) and Tb4 (12,12−y  ,34) form a collinear structure with the (+ + − −) sequence in the crystallographic unit cell for the first component and (− + + −) for the second.Figure optionsDownload as PowerPoint slide