Structural Distortion Drives Magnetic Ordering in Halide Double Perovskites

Halide double perovskites are promising candidates for spintronic and multiferroic applications due to their coupled structural and magnetic properties [1-2]. Using neutron diffraction and magneto-Raman spectroscopy, we reveal a contrasting magneto-structural relationship in Cs₂NaFeCl₆ and Cs₂AgFeCl₆. Cs₂NaFeCl₆ retains a cubic structure with geometrically frustrated antiferromagnetism (AFM) and a low Néel temperature (T_N ≈ 3.4 K). Conversely, Cs₂AgFeCl₆ undergoes a cubic-to-tetragonal distortion (Fm-3m to I4/mmm) concurrent with AFM ordering at T_N ≈ 19 K. This distortion relieves magnetic frustration, resulting in distinct AFM order (type-III for Na and type-I for Ag). Our results demonstrate the crucial role of structural engineering in tailoring the magnetic properties of halide perovskites for next-generation spin-optoelectronic devices.

References
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2.Mopoung, K. et al. Understanding Antiferromagnetic Coupling in Lead-Free Halide Double Perovskite Semiconductors. J. Phys. Chem. C 128, 5313–5320 (2024).