Elastic and magnetoelastic constants of Y3-xFe5+xO12 garnets: polycrystalline-to-single crystalline approximations

Abstract

The growth and characterization of single crystalline materials require considerable experimental expertise and cumbersome evaluation. Estimating the physical properties of single crystals from their polycrystalline counterparts is a topic of considerable scientific interest. A close agreement between elastic theory-derived zero-porosity-corrected values of longitudinal (L₀) and rigidity modulus (G₀) for polycrystalline Y₃Fe₅O₁₂ and longitudinal (C₁₁) and shear (C₄₄) stiffness constants for single crystalline equivalent has been found. This prompted the approximation of elastic, magnetoelastic, and magnetostriction constants for single crystalline analogs of the garnet series Y_3-xFe_5+xO₁₂, with x = 0.0, 0.1, 0.3, and 0.5. The elastic stiffness constants (C₁₁, C₁₂, and C₄₄), magnetoelastic coupling constants (b₁ and b₂), and interatomic force constant (f) are found to decrease. The elastic compliance constants (S₁₁, S₁₂, and S₄₄) are found to increase while magnetostriction constants (λ₁₀₀, λ₁₁₁, λ₁₁₀) and λ_S show random variations with Fe³⁺ substitution. The Cauchy pressure (P_c) monotonically increases for x = 0.1–0.5 compositions. The results have been explained based on the large size and magnetic moment mismatch of Y³⁺ (0.89 Å, 0 μ_B)- and Fe³⁺ (0.645 Å, 5 μ_B)-induced structural and electronic distortions, lattice strain, and antisite disorder. In addition to qualitative analysis, quantitative analysis to explain the variation of λ₁₁₁ and f versus x has been given.

Graphical abstract