Magnetic nanoparticles demonstrate magnetic properties attractive for data storage, spintronics, and biomedical applications. On the nanoscale, disorder effects crucially determine the magnetic properties such as the relaxation dynamics and magnetic hyperthermia performance of magnetic nanoparticles [1].
Despite the technological relevance and fundamental importance, a quantitative interpretation of the three-dimensional spin structure remains a key challenge. Small-angle neutron scattering is a powerful technique for investigating on length scales between about 1 − 100 nm the structure and dynamics of magnetic materials, like skyrmions in chiral magnets, shape-memory alloys, Nd-Fe-B based permanent magnets, and ferrofluids [2].
In this seminar, I will demonstrate how magnetic-field-dependent SANS in combination with micromagnetism allows to access quantitative information on the spin structure of magnetic nanocrystals in different media, as in dispersion, densely packed powder or bulk metallic alloy. Empowered with micromagnetics, SANS can reveal the transition from a single-domain to a multidomain state in nanoparticles [3] and separate surface spin disorder from intra-particle disorder contributions
[1] P. Bender et al., J. Phys. Chem. C, Vol. 122, 3068 (2018).
[2] S. Mühlbauer, D. Honecker, E. A. Périgo, F. Bergner, S. Disch, A. Heinemann, S. Erokhin, D. Berkov, C. Leighton, M. Eskildsen, A. Michels, Rev. Mod. Phys. 91, 015004 (2019).
[3] L. G. Vivas, R. Yanes, D. Berkov, S. Erokhin, M. Bersweiler, D. Honecker, P. Bender, and A. Michels, PRL 125, 117201 (2020). [4] D. Zákutná, D. Nižňanský, L.C. Barnsley, E. Babcock, Z. Salhi, A. Feoktystov, D. Honecker, S. Disch, PRX 10, 031019 (2020).
Dr. Christian Franz
Dr. Christian Lang