Magnetic properties of ErAg

Neutron diffraction data from a powder sample of ErAg show two antiferromagnetic transitions at temperatures of 18 ± 1 K and 9.5 ± 0.5 K. The magnetic superlattice reflections for the two structures can be indexed on a tetragonal magnetic cell which has basal plane edges twice that of the chemical cell (a_m = 2a₀) and the same dimension in the unique c‐axis direction (c_m = c₀). Between 18 and 9.5 K the magnetic ordering is similar to HoAg and conforms to a sinusoidally modulated magnetization wave propagating in the $\text{〈100〉}$ direction with the moments tilted from the c axis at angles ranging from 40° (at 18 K) to 80° (at 10 K). The modulation wavelength of 53 ± 2 Å (7.4a_m) is incommensurate with the unit chemical cell and is temperature independent. In this incommensurate ordering region the ordered moment increases with decreasing temperature to a maximum value of 6.8μ_B at T = 10 K. Below 9.5 K, the antiferromagnetic ordering is a commensurate (+ − + −) layer‐type structure similar to that of DyAg and TbAg, in which adjacent (110) ferromagnetic planes have oppositely directed moments. The tilt of the moments from the c axis is 85° at T = 9 K and decreases to 75° at T = 4 K. The ordered moment on the Er atom sites is 7.2 ± 0.2μ_B at T = 4 K.