NEUTRON-DIFFRACTION STUDY OF C-14-LAVES-PHASE, TBMN2 AND DYMN2

The temperature dependence of powder neutron diffraction for hexagonal C14-Laves-phase TbMn2 and DyMn2 has been measured. Ferromagnetism and antiferromagnetism coexist in TbMn2. The ferromagnetic component cont inues up to 60 K, whereas the antiferromagnetic component takes its ma ximum value at around 55 K, begins to decrease above 55 K and vanishes at around 80 K. The magnetic unit cell of the antiferromagnetism is t wice of the chemical one in an a-direction. A presumable magnetic stru cture has been discussed. For C14-DyMn2, no other structure is observe d except for the ferromagnetic one which disappears at around 35 K.