Intense ferromagnetic fluctuations preceding magnetoelastic first-order transitions in giant magnetocaloricLaFe13−xSix,Physical Review Materials

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Intense ferromagnetic fluctuations preceding magnetoelastic first-order transitions in giant magnetocaloricLaFe13−xSix
Physical Review Materials ( IF 3.1 ) Pub Date : 2021-07-22 , DOI: 10.1103/physrevmaterials.5.l071401
Zhao Zhang _{1,

2} , Houbo Zhou _{3,

4} , Richard Mole ₅ , Chenyang Yu _{1,

2} , Zhe Zhang _{1,

2} , Xinguo Zhao ₁ , Weijun Ren ₁ , Dehong Yu ₅ , Bing Li _{1,

2} , Fengxia Hu _{3,

4} , Baogen Shen _{3,

4} , Zhidong Zhang _{1,

2}

Affiliation

First-order magnetic transitions are of both fundamental and technological interest given that a number of emergent phases and functionalities are thereby created. Of particular interest are giant magnetocaloric effects, which are attributed to first-order magnetic transitions and have attracted broad attention for solid-state refrigeration applications. While the conventional wisdom is that atomic lattices play an important role in first-order magnetic transitions, a coherent microscopic description of the lattice and spin degrees of freedom is still lacking. Here, we present a comparative neutron scattering study on the lattice and spin dynamics in intermetallic

La {Fe}_{11.6} {Si}_{1.4}

and

La {Fe}_{11.2} {Si}_{1.8}

, which represent one of the most classical giant magnetocaloric systems and undergo first-order and second-order magnetic transitions, respectively. While their spin-phonon coupling effects are quite similar,

La {Fe}_{11.6} {Si}_{1.4}

exhibits a much stronger magnetic diffuse scattering in the paramagnetic state preceding its first-order magnetic transition, corresponding to intense ferromagnetic fluctuations. These dynamic insights suggest that the magnetic degree of freedom dominates this magnetoelastic transition and ferromagnetic fluctuations might be universally relevant for this kind of compounds.

中文翻译：

巨磁热LaFe13−xSix中磁弹性一阶跃迁之前的强烈铁磁波动

鉴于由此产生了许多涌现阶段和功能，一阶磁跃迁具有基础和技术意义。特别令人感兴趣的是巨磁热效应，它归因于一阶磁跃迁，并引起了固态制冷应用的广泛关注。虽然传统观点认为原子晶格在一阶磁跃迁中起着重要作用，但仍然缺乏对晶格和自旋自由度的连贯微观描述。在这里，我们对金属间化合物的晶格和自旋动力学进行了比较中子散射研究。