NEUTRON-DIFFRACTION STUDY OF MAGNETIC-PROPERTIES OF TMCO2

The present neutron diffraction studies have confirmed that TmCo2 repr esents an exception within the RCo(2) series. It was found that, in co ntrast with other heavy RCo(2) compounds, the Co sublattice in TmCo2 d oes not order magnetically below the Curie temperature (T-C = 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 i nduce magnetic order within the Co sublattice, as is the case in other RCo(2) compounds. Furthermore, we show that the magnetic structure an d the onset of long-range order in TmCo2 depend sensitively on the sam ple preparation, which partly explains the differing results published earlier.