High-Pressure Synthesis and Physical Properties of a Spinel Compound FeAl₂S₄

Abstract

A spinel compound FeAl2S4 was successfully synthesized under high-pressure and high-temperature conditions and was systematically characterized via the structural, magnetic, and specific heat measurements. It crystallizes into a cubic structure with the space group Fd3̅m (no. 227) and the lattice constant a = 10.0207(2) Å. A Fe/Al site inversion is found; that is, the molecular formula can be rewritten as (Fe1–x Al x )­(Al2–x Fe x )­S4, and the inversion parameter x is about 0.22. Magnetic susceptibility measurements indicate that FeAl2S4 undergoes a spin glass behavior, which is confirmed by ac susceptibility and specific heat measurements. The freezing temperature T f ∼ 10.5 K and Weiss temperature T θ ∼ −107.4 K lead to a high frustration parameter f = |T θ/T f| of about 10, which suggests that FeAl2S4 is a high-frustration magnet. Our results indicate that high pressure can help stabilize the spinel structure with small R̅ σ and the cation inversion plays an important role in the formation of the spin glass state.

High-Pressure Synthesis, Crystal Structure, and Physical Properties of a Spinel Compound Co0.7Al2S4

“…The isothermal magnetization measurements on Co 0.7 Al 2 S 4 were carried out at 2 and 20 K, and the obtained curves are plotted in Figure b. The magnetization dependence of magnetic field at 20 K is linear, while the isothermal magnetization curve at 2 K exhibits little magnetic hysteresis with a small coercive force but nonsaturated magnetization behavior, shown in the inset of Figure b, which is also common in a spin glass system. , …”

“…The details are described in ref 19. 19 The goodness-of-fit parameter χ 2 which was obtained by Rietveld refinements of the PXRD, as a function of inversion parameter η is displayed in Figure 3b.…”

“…The powder X-ray diffraction (PXRD) of the sample was measured and is plotted in Figure 2. The result shows that the main diffraction peaks can be indexed using a cubic spinel structure like FeAl 2 S 4 , 19 but an obvious impurity phase of Co 1−x S is included, 20 which is denoted by the green asterisks also as shown in Figure 2. Then, we tried to decrease the content of Co and carried out the synthesis to prepare the pure compound, of which the details are the same as the above.…”

“…Fortunately, FeAl 2 S 4 with a spinel structure is successfully prepared at high pressure. It is reported to be a spin-liquid candidate, but a cation inversion results in a spin glass behavior, freezing at ∼10.5 K, which inspires researchers to explore other more Al-based spinel sulfides . In this paper, we also set out to conduct an exploratory work at high pressure and report the synthesis, crystal structure, and physical properties on the Al-based spinel sulfide Co 0.7 Al 2 S 4 .…”

LaAeAl3S7(Ae = Ca, Sr): Cairo pentagonal layered thioaluminates achieving a good balance between a strong second harmonic generation response and a wide bandgap

“…S3a and b †). Note that 2D (AlS 4 ) n layers were also rarely discovered and only a few ternary thioaluminates exhibit 2D layered structures, such as FeAl 2 S 4 , 53 TlAlS 2 54 and AeAl 2 S 4 55 (Ae = Ca, Sr). Although they have layered structures, the link modes of their AlS 4 units are different to those in the title LaAeAl 3 S 7 (Fig.…”