Vivas Laura G, Yanes Rocio, Berkov Dmitry, Erokhin Sergey, Bersweiler Mathias, Honecker Dirk, Bender Philipp, Michels Andreas
Department of Physics and Materials Science, University of Luxembourg, 162A avenue de la Faïencerie, L-1511 Luxembourg, Grand Duchy of Luxembourg.
Department of Applied Physics, University of Salamanca, Salamanca 37008, Spain.
Phys Rev Lett. 2020 Sep 11;125(11):117201. doi: 10.1103/PhysRevLett.125.117201.
In the quest to image the three-dimensional magnetization structure we show that the technique of magnetic small-angle neutron scattering (SANS) is highly sensitive to the details of the internal spin structure of nanoparticles. By combining SANS with numerical micromagnetic computations we study the transition from single-domain to multidomain behavior in nanoparticles and its implications for the ensuing magnetic SANS cross section. Above the critical single-domain size we find that the cross section and the related correlation function cannot be described anymore with the uniform particle model, resulting, e.g., in deviations from the well-known Guinier law. In the simulations we identify a clear signature for the occurrence of a vortexlike spin structure at remanence. The micromagnetic approach to magnetic SANS bears great potential for future investigations, since it provides fundamental insights into the mesoscale magnetization profile of nanoparticles.
在对三维磁化结构进行成像的探索中，我们表明磁小角中子散射（SANS）技术对纳米颗粒内部自旋结构的细节高度敏感。通过将SANS与数值微磁计算相结合，我们研究了纳米颗粒中单畴到多畴行为的转变及其对随后的磁SANS截面的影响。在临界单畴尺寸以上，我们发现截面和相关的关联函数不再能用均匀颗粒模型来描述，例如，这会导致偏离著名的吉尼尔定律。在模拟中，我们确定了剩余状态下出现涡旋状自旋结构的明显特征。磁SANS的微磁方法在未来的研究中具有巨大潜力，因为它能为纳米颗粒的中尺度磁化分布提供基本见解。
