Poudeu group's findings could shed light on new ways to create high-Tc ferromagnetism in semiconductors

Poudeu group's findings could shed light on new ways to create high-Tc ferromagnetism in semiconductors

MSE is pleased to announce that Associate Professor P. Ferdinand P. Poudeu group’s manuscript, "Engineering Magnetic Transitions in Fe1−xSnxBi2Se4 n‑Type Ferromagnetic Semiconductors through Chemical Manipulation of Spatial Separation between Magnetic Centers," was recently published in Chemistry of Materials, the flagship materials chemistry journal of the American Chemical Society (ACS).

According to Poudeu, this paper unambiguously settles the debate around the intrinsic role of concentration of the magnetic atom and separation between magnetic center in tuning the temperature of transition from ferromagnetic behavior to paramagnetic regime, the so-called Curie temperature.

“Our study suggests that separation between magnetic centers rather than the concentration of magnetic atoms controls the magnitude of the Curie transition temperature in ferromagnetic semiconductors,” Poudeu said. “Large separation between magnetic centers leads to a drop in the Curie temperature.”

This conclusion could be extremely useful in the field of diluted magnetic semiconductors (DMSs) when designing high Tc materials based on conventional semiconductors such as GaAs, ZnSe, etc.  

Abstract:

Understanding the nature and origin of high-temperature ferromagnetic-like ordering in complex semiconducting transition metal selenides, such as FeBi2Se4, is extremely important and could shed light on novel approaches to develop high-Tc ferromagnetism in traditional semiconductors. Here, we report on the effect of partial substitution of Fe by Sn on the distribution of magnetic centers within the Fe1–xSnxBi2Se4 crystal lattice and its impact on the electronic and magnetic properties. Several compositions of the Fe1–xSnxBi2Se4 (0.1 ≤ x ≤ 0.5) solid solution were synthesized by combining high-purity elements in the respective stoichiometric ratios. Powder X-ray diffraction suggests that the synthesized phases are isostructural with the parent compound, FeBi2Se4, despite the large difference in the ionic radii of Fe2+ and Sn2+ in octahedral coordination. Single-crystal X-ray diffraction reveals increased ordering in the distribution of Fe2+, Sn2+, and Bi3+ atoms in various metal sites within the crystal structure, with full atomic ordering reached for the Fe0.5Sn0.5Bi2Se4 (x = 0.5) composition. High-temperature direct current (dc) magnetic susceptibility measurements reveal that all Fe1–xSnxBi2Se4 samples remain ferromagnetic over a wide temperature range and the Curie transition temperature, Tc, decreases from ∼450 K for compositions with x ≤ 0.15 to 325 K for compositions with high Sn content. The observed drop in Tc is ascribed to an increased separation between the magnetic centers for compositions with x > 0.15. Hall effect measurements confirm the n-type semiconducting nature of all compounds. Interestingly, the carrier density of Fe1–xSnxBi2Se4 samples gradually decreases with decreasing temperature down to 150 K, below which a remarkable transition from semiconducting to metallic behavior is observed for compositions with x ≥ 0.25.

Read the full article here.

Other recently published articles by the Poudeu group:

"Coherent Magnetic Nanoinclusions Induce Charge Localization in Half-Heusler Alloys Leading to High-Tc Ferromagnetism and Enhanced Thermoelectric Performance"

"Charge Disproportionation Triggers Bipolar Doping in FeSb2–xSnxSe4 Ferromagnetic Semiconductors, Enabling a Temperature-Induced Lifshitz Transition"