Magnetic properties of the singlet antiferromagnet KTb(WO4)2

X-ray studies of the magnet KTb(WO4)2 have shown that this compound belongs to the monoclinic class C2∕c with a chain structure. The susceptibility and magnetization of KTb(WO4)2 single crystals are investigated experimentally in the temperature region 0.4–100 K and at magnetic fields up to 2 T. The angular dependence of the susceptibility shows that at low temperatures a purely Ising anisotropy is realized in this compound: there exists but one component of the moment, along the b axis. The temperature dependence of the susceptibility has a maximum at T=1.2K, and the M(H) curve obtained at 0.5 K exhibits substantial nonlinearity at low fields, as is characteristic of an ordered state. Analysis of the experimental data in the mean field approximation suggests that this state is a singlet Ising antiferromagnet with TN≈0.7K, a value determined from the susceptibility data. At extremely low temperatures a collinear antiferromagnetic structure with equivalent sublattices is realized in the sample, according t...