Neutron diffraction study of magnetic properties of TmCo2

The present neutron diffraction studies have confirmed that TmCo2 represents an exception within the RCo2 series. It was found that, in contrast with other heavy RCo2 compounds, the Co sublattice in TmCo2 does not order magnetically below the Curie temperature (TC=3.9 K). This is assumed to be due the fact that in TmCo2 the intersublattice (f-d) molecular field is smaller than the critical field necessary to induce magnetic order within the Co sublattice, as is the case in other RCo2 compounds. Furthermore, we show that the magnetic structure and the onset of long-range order in TmCo2 depend sensitively on the sample preparation, which partly explains the differing results published earlier. (orig.)