# Neutron scattering shows quasi-two-dimensional magnetic transition in layered Y₁₋ₓTbₓMn₆Sn₆, 300–353 K

- Published: 2026-11-13 23:14 UTC
- Section: Science › Physics
- Tags: small-angle neutron scattering, layered magnetic compounds, Y₁₋ₓTbₓMn₆Sn₆, magnetic phase transition, critical temperature, incommensurate magnetic structure, critical fluctuations, terbium doping, manganese layers
- URL: https://realtech.media/news/rt-4f30ad4c7c2f2a91882aaad7_neutron_scattering_shows/

**Physicists from Russia and Egypt used small-angle neutron scattering to trace how layered Y₁₋ₓTbₓMn₆Sn₆ magnets lose order when heated above the critical temperature.**

![Neutron scattering shows quasi-two-dimensional magnetic transition in layered Y₁₋ₓTbₓMn₆Sn₆, 300–353 K](https://realtech.media/media/2026/11/8478578d881b0a4c.jpg)
*U.S. Department of Energy from United States, Wikimedia Commons, Public domain*

A team of scientists from Russia and Egypt has studied how the layered magnetic compounds Y₁₋ₓTbₓMn₆Sn₆ pass from magnetic order to disorder, according to «Поиск» (Poisk) [1]. The researchers used small-angle neutron scattering on three compositions, one without terbium and two with terbium added. Measurements covered 260 to 400 K, below and above the critical temperature [1]. The results were published in the Journal of Experimental and Theoretical Physics (JETP) [1].

In these materials, manganese atom layers have strong magnetic order within the plane, while bonds between layers are much weaker. Because of this nearly two-dimensional architecture, the transition on heating is more complex than in ordinary three-dimensional magnets. The system does not demagnetize as a whole but breaks up into fluctuating ferromagnetic planes [1]. A neutron beam is sensitive to magnetic moments and reveals not single atoms but larger magnetic inhomogeneities, domains and fluctuations.

## Critical temperature and magnetic structure

Three contributions were separated in the scattering: scattering from large-scale magnetic domains, a Bragg peak from an incommensurate magnetic structure whose period does not match the crystal lattice period, and scattering from critical fluctuations of magnetization [1].

The critical temperature rises with terbium content: about 300 K for the pure compound, about 325 K for x = 0.10 and about 353 K for x = 0.25 [1]. The magnetic structure changes as well. Pure YMn₆Sn₆ has a complex double planar spiral, while the doped compositions show a ferrimagnetic component and a conical spiral. The period of the incommensurate structure grows with terbium concentration [1].

Terbium also shifts the balance of magnetic anisotropy. States with an easy axis and an easy plane compete, so the system passes through several magnetic configurations as temperature changes [1].

## Fluctuating planes above the transition

Above the critical temperature, the magnetic structure does not fall apart into fully independent moments. It breaks into fluctuating ferromagnetic manganese planes: order within a plane is largely preserved, while coherence between planes is already lost. This gives the transition a quasi-two-dimensional character [1].

The size of regions where magnetic moments remain coherent is limited to about 14 Å in the pure compound and about 28 Å in the doped ones. At around 400 K it falls to 4–5 Å, practically the thickness of one manganese layer [1]. Below the critical temperature, critical scattering decays quickly, and an ordered phase forms with large-scale magnetic domains and an incommensurate spin structure [1].

The study was carried out by staff of the Konstantinov Petersburg Nuclear Physics Institute of the Kurchatov Institute, the Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences, the Joint Institute for Nuclear Research and the Nuclear Research Center of the Egyptian Atomic Energy Authority [1].

## Sources

1. [Поиск](https://poisknews.ru/fizika/magnitnye-sloi-zhivut-svoej-zhiznyu-nejtronnoe-rasseyanie-raskrylo-neobychnyj-fazovyj-perehod)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-4f30ad4c7c2f2a91882aaad7_neutron_scattering_shows/