Growth of a hexagonal α-Fe1−xCrxSe (x ≥ 0.4) alloying phase with room-temperature high coercivity by Cr introduction

Abstract

3d transition metal chalcogenides have gradually become candidates for magnetic materials due to their unique d-electronic structures. However, a relatively lower Curie temperature (TC) and coercivity (HC) limit their widespread applications. Here, we report a high-temperature organic-solvent-phase method for the synthesis of hexagonal α-Fe1−xCrxSe (0 ≤x ≤ 0.6) alloyed nanosheets with high TC through Cr introduction. Without Cr introduction, FeSe nanosheets appear as a mixture of tetragonal β-FeSe and hexagonal α-FeSe phases with a soft/hard decoupled hysteresis loop of HC∼3.35 kOe at 5 K. With an increase in the Cr content, α-Fe1−xCrxSe gradually becomes dominant. The tetragonal-to-hexagonal phase transition is completed at the optimum doping of Cr (x = 0.4), and α-Fe1−xCrxSe exhibits hard magnetic behavior. The coercivity (HC) can be as high as 15.80 kOe at 5 K and 4.98 kOe at 300 K when the Cr concentration reaches 60%. The synthesis of α-Fe1−xCrxSe alloy provides a potential material for hard magnets. Therefore, the doping-induced phase transition is an effective way to synthesize ideal phase nanomaterials.