Composés isomorphes MeX2O4: Dilatation thermique anisotrope et ordre magnétique dans MnSb2O4

Using X-ray diffraction data, the anisotropic thermal expansion coefficients α_a and α_c of two isomorphic compounds MnSb₂O₄ and NiSb₂O₄ are linked to the anisotropic elastic constants of these tetragonal structures and compared to the ZnSb₂O₄, SnPb₂O₄ thermal expansion coefficients. The anomalous thermal expansion observed for MnSb₂O₄ in the 6–115 K range (maximum of α_c at 70 K) is related to the ordering of Mn²⁺ ion magnetic moments. Using neutron diffraction, two kinds of antiferromagnetic order are observed for MnSb₂O₄ and NiSb₂O₄. At 6 K the value of the resultant moment is approximately 1.8 μ_B for NiSb₂O₄ and 3.8 μ_B for MnSb₂O₄. A critical temperature of T_c = 115 K is proposed for MnSb₂O₄ based on the use of X-ray diffraction data alone.