Re-entrant ferrimagnetism in HfFe6Ge6-type TmMn6Sn6-xInx (0.2 <= x <= 1.6)and ErMn6Sn6-xInx (0.1 <= x <= 1.0) solid solutions

The TmMn6Sn6-xInx (0.2 less than or equal tox less than or equal to1.6) and ErMn6Sn6-xInx (0.1 less than or equal tox less than or equal to1.0) compou nds have been prepared and studied by powder magnetization measurements. Th e In-rich compounds (x(In)greater than or equal to0.5 for Tm and x(In)great er than or equal to0.2 for Er) are ferrimagnetic in their whole ordered ran ge with Curie temperatures ranging between 342 and 253 K. The TmMn6Sn5.8In0 .2 compound displays a Met point at 321 K and undergoes a ferrimagnetic tra nsition at 48 K. The TniMn(6)Sn(5.6)In(0.4) and ErMn6Sn5.9In0.1 compounds d isplay re-entrant ferrimagnetism. They are characterized by a large increas e in the magnetization at the ordering point (T approximate to 322 and 342 K, respectively), a transition to an antiferromagnetic state at lower tempe rature (T approximate to 264 and 319 K, respectively) and finally by a tran sition to a ferrimagnetic state at lower temperature (T approximate to 111 and 141 K, respectively). In their antiferromagnetic states they display a metamagnetic behaviour (H(1)less than or equal to3.2 kOe). At low temperatu re all the compounds studied do not display large magnetocrystalline anisot ropy. These results are discussed and compared with those related to the RM n6Sn6 and RMn6Ge6-xGax compounds (R=Er, Tm). (C) 2001 Elsevier Science B.V. All rights reserved.