Cation Disorder and Magnetic Properties of Certain Garnet Type Crystals

Abstract

The garnet of composition Bi_3−2xCa_2xFe_5−xV_xO₁₂ (BiCaVIG) is derived from the well known yttrium iron garnet (YIG) wherein Y³⁺ ions are completely replaced by a combination of Ca²⁺ and Bi³⁺ ions and Fe³⁺ ions are partly substituted with V⁵⁺ ions ^{(1, 2)}.Though BiCaVIG is isostructural to YIG one can expect a certain amount of difference between the crystal fields in the crystallographic sites in these two compounds. One way to study the crystal fields would be to study and compare the magnetic behaviour of a paramagnetic ion when present in these two crystals, as it is well known that the energy levels of an ion are perturbed by the crystal field and its symmetry. Further one can also expect that the presence of cations of different chemical nature as in the BiCaVIG lattice to modify the energy levels as it will be shown later. In this work we will describe the magnetic properties of some paramagnetic ions such as Co²⁺ (3d⁷), Ru³⁺ (4d⁵) and Tb³⁺ (4f⁸), when they are doped in BiCaVIG crystals and compare the results with those obtained when they are present in YIG crystal. Such differences in behaviour could tell us about the sites wherein are present the paramagnetic ions.