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arXiv · 2610.17292

Phase-Coherent Spin and Lattice Modulations in a Y-type Hexaferrite

Oskar Stepančić·Annika Stellhorn·Emma Campillo·Kun Zhai·Niklas Ekström·A. Corani·D. Alba Venero·R. Cubitt·E. Blackburn·L. Shen
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Abstract

Spin-driven multiferroics owe their electric polarization to lattice distortions that follow the magnetic order, yet in incommensurate magnets symmetry normally forbids such a distortion at the fundamental magnetic wavevector, and the distortions themselves are rarely observed. Here we use half-polarized neutron scattering to show that the Y-type hexaferrite Ba$_{0.4}$Sr$_{1.6}$Mg$_2$Fe$_{12}$O$_{22}$ hosts, in its saturated high-field state, a magnetic modulation and a longitudinal lattice modulation at one and the same wavevector, locked in phase. The signature is a large nuclear-magnetic interference asymmetry, $r$ ~ 0.8, of the same sign at the two conjugate satellites and persisting to 275 K. The zone contrast and the field dependence of the satellite indicate an internal, field-induced longitudinal distortion. The modulated state coexists with the transverse-conical magnetoelectric phase and outlives it, revealing a fundamental-wavevector spin-lattice coupling in a magnetic field regime previously regarded as a simple ferrimagnet.

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Oskar Stepančić, Annika Stellhorn, Emma Campillo, Kun Zhai, Niklas Ekström, A. Corani, D. Alba Venero, R. Cubitt, E. Blackburn, L. Shen. 2026-10-12. Phase-Coherent Spin and Lattice Modulations in a Y-type Hexaferrite. https://arxiv.org/abs/2610.17292

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