Magnetic Structure of HoAg2

Abstract

The tetragonal body‐centered HoAg₂ has been shown by neutron powder diffraction to become an anti‐ferromagnet with the Néel temperature of 5.7°K. The magnetic spin alignment is represented by a static longitudinal wave propagating along the $a$ axis of the face‐centered alternative of the chemical lattice. The wavelength of this static spin wave is 1.21 times (the face‐centered $a$ spacing), being incommensurable with the lattice repetition. Below 4.6°K, a linear–transverse spin wave being polarized in the c‐axis direction develops with the propagation direction and wavelength identical to the coexisting longitudinal wave. The maximum and rms moments in Bohr magnetons extrapolated to 0°K are, respectively, 7.5 and 5.3 for the longitudinal wave and 5.0 and 3.5 for the transverse wave. The maximum composite moment at 0°K is ${\text{9.0\hspace{0.17em}±\hspace{0.17em}0.2 μ}}_B$ , while the free Ho³⁺ ion should yield ${\text{10 μ}}_B$ .