MAGNETIC STRUCTURE OF TBAG2

Neutron-diffraction measurements have revealed that TbAg2 having the tetragonal CaC2-type structure becomes antiferromagnetic below the Néel temperature of 35°K. The ordered magnetic structure consists of the ferromagnetic sheets which are perpendicular to the a axis (face-centered description), and the moment directions of the adjacent ferromagnetic sheets are opposite to one another. All moments are aligned in the direction of the c axis, and the saturation moment per Tb is 8.95±0.05 Bohr magnetons which is essentially equal to the ordered moment of the free Tb3+ ion. This ordered structure is identical to the commensurable magnetic structure of TbAu2 at temperatures below 42.5°K, but the incommensurable transverse-wavelike spin alignment of TbAu2 found in the 42.5°-55°K range was not detectable in TbAg2. Also, no detectable moment is observed for Ag in TbAg2.