MAGNETIC-PROPERTIES OF SCMN6SN6, YMN6SN6, GD-TMMN6SN6, LUMN6SN6 COMPOUNDS WITH HFFE6GE6 TYPE-STRUCTURE

Ternary stannides RMn6Sn6 (R = Sc, Y, Gd-Tm, Lu) have been synthesized from the elements. All the compounds are isotypic and crystallize in the HfFe6Ge6 type structure (filled derivative of CoSn-B35). Their magnetic behaviours were studied in the temperature range 4.2 K < T < 900 K. All these compounds order ferrimagnetically (Gd-Ho) or antiferromagnetically (Sc, Y, Er, Tm, Lu), up to rather high temperatures (333 K < T < 435 K). With R = Gd-Ho, both R and Mn sublattices order simultaneously above the room temperature while Er and Tm sublattices order only at 75 and 58 K respectively. RMn6Sn6 compounds with R = Tb-Ho exhibit a second magnetic transition below the Curie point, related to a reorientation of the easy axis magnetization, from the basal plane to the c axis. Some of these compounds (Tb-Er) exhibit large coercive fields (up to 11 kOe for TbMn6Sn6 at 4.2 K) related to uniaxial anisotropy.