Magnetic thermodynamics as proxy for chemical inhomogeneity in hemo-ilmenite solid solutions

Abstract

In this study, we present ac susceptibility measurements for a synthetic and a natural hemo-ilmenite (HI) solid solution (x)FeTiO 3-(1x)Fe 2 O 3 with compositions x = 0.87(1) and 0.88(8), respectively. The focus of the investigation is the magnetic ordering at the Curie temperature T C and the spin-glass-like freezing at the freezing temperature T f. The sharpness of T C for the synthetic solid solution with well-defined structure indicates the chemical homogeneity of the solution, whereas the disperse magnetic ordering of the natural solid solution reveals inhomogeneities described as spin glass system ofvariations in composition x. The frequency dispersion of T f was determined between 10 Hz and 10 kHz and was found to obey a dynamic scaling power law. The relaxation rates deviate by five orders of magnitude where the synthetic solid solution exhibits x 0 = 3(1) 9 10 4 Hz and the natural one 5.5 9 10 9 Hz. The strong deviation is attributed to the difference in the ordered state above T f. These findings provide an insight into the cooling-rate effects of natural solid solutions and how magnetic thermodynamics can be used to probe the chemical homogeneity of such systems.

Large spontaneous magnetostriction in FeTiO3and adjustable magnetic configuration in Fe(III)-doped FeTiO3

“…The crystal and magnetic structure of FeTiO 3 ilmenite and its solid solutions with Fe 2 O 3 hematite have attracted considerable interest in physics, [22][23][24][25][26] the Earth sciences, [27][28][29] and materials science. 30,31 The compound FeTiO 3 is an antiferromagnet with a Néel temperature of T N = 58(1) K 23 and a semiconductor with a measured band gap of E g = 2.5 eV.…”