Magnetic Structures of TbAu2

Abstract

Neutron‐powder‐diffraction study has shown that, in the range 55°‐42.5°K, TbAu₂ (tetragonal, iso‐structural to MnAu₂) exhibits a linear‐transverse‐wave spin alignment propagating along the $a$ axis (the face‐centered description) and polarized in the $c$ axis direction. The wavelength of this static magnetization wave is incommensurable with the atomic repetition and varies 1.200‐1.186 in $a$ spacing units in the range 55°‐42.5°K. The rms moment per Tb at 42.6°K is 5.1 Bohr magnetons. At just below 42.5°K, a first‐order magnetic transition takes place and the wavelength of the transverse wave abruptly becomes equal to the $a$ spacing. The resulting antiferromagnetic structure persists down to 2°K and the saturation moment is practically identical to the ordered moment of the free Tb³⁺ ion, 9.0 Bohr magnetons. The crystallographic data in the range 300°‐5°K are also presented.