Magnetism of singlets in terbium molybdate

Abstract The magnetization was measured in a single crystal sample of the orthorhombic ferroelectric paramagnetic β′-Tb2(MoO4)3 along the [0 0 1], [0 1 0] and [1 0 0] axes in the magnetic field up to 19 T at 4.2 K T K . An expression for the field and temperature dependence of the magnetization M(H,T) along the main directions was derived using the theory of the magnetism of singlets. Three lowest singlets of the spectrum of Tb3+ ion in β′-Tb2(MoO4)3 were taken into account. The existence of two types of sites for Tb3+ ions in β′-Tb2(MoO4)3 was taken into account. Magnetization curves were calculated by fitting this expression to the experimental curves. The results of the calculations agree with the experiment satisfactorily at low temperatures. As the results of fitting the saturation magnetic moments of Tb3+ ions at nonequivalent sites were found for three main directions. Their relative values reflect the symmetry of the nearest surrounding of Tb3+ ions.