NMR determination of noncollinear antiferromagnetic structure in TbCoGa

Tokunaga, Yo  ; Saito, Yo*; Sakai, Hironori   ; Kambe, Shinsaku  ; Sanada, Naoyuki*; Watanuki, Ryuta*; Suzuki, Kazuya*; Kawasaki, Yu*; Kishimoto, Yutaka*

We report NMR studies of TbCoGa, which has the tetragonal HoCoGa structure and exhibits two antiferromagnetic (AF) transitions at =36.2 K and =5.4 K. From a symmetry analysis of internal magnetic fields at orthorhombic Ga sites, we have successfully determined the magnetic structures in the AF-I () and AF-II () phases. The AF-I phase is a collinear AF order with a propagation vector and ordered moments parallel to the [001] direction. In the AF-II phase, on the other hand, we found a non-collinear AF structure described by double propagation vectors and , where the moments tilt away from the [001] direction toward [100], keeping a constant value along the [001] direction. In the context of these results we discuss the possible presence of magnetic frustration in this system.