Tailoring magnetic nanoparticles (NPs) by choosing a suitable combination of size, shape, and material is the basis for realizing various technological (data storage, spintronics)[1], biomedical (magnetic hyperthermia, drug delivery)[2], or environmental applications. The macroscopic physical properties of magnetic NPs rely on magnetic anisotropy, and their understanding is fundamental to the
design of magnetic materials for different applications. Nevertheless, magnetic anisotropy is influenced by the shape, crystal structure, surface effects, and interactions. To gain a comprehensive understanding of these properties, it is essential to investigate all the factors contributing to the total effective magnetic anisotropy. Conventional magnetic measurements like DC magnetization and AC susceptibility provide an overview of the macroscopic physical properties but do not reveal the detailed microscopic phenomena that drive these properties. This is where small-angle polarized neutron scattering (SANSPOL) comes into play, offering sub-atomic resolution and serving as a powerful tool for studying surface anisotropy[3] and microscopic phenomena.
In this contribution, we will show the impact of the Mn-doping level in cobalt ferrite NPs (10 nm) on their magnetic properties. Nevertheless, the macroscopic magnetic responses of the Mn-mixed cobalt ferrite NPs were inconclusive and inconsistent with changing Mn content. However, we will demonstrate the versatility of SANSPOL and disentangle all anisotropy contributions of the total
magnetic anisotropy of a series of Mn-mixed Cobalt ferrite NPs with different Mn content but the same shape, size, and surfactant and correlate it with their macroscopic response[4]. Ultimately, our work aims to clarify the complicated picture of magnetic anisotropy and offer insights into the design of magnetic materials.
The authors thank ISIS Neutron and Muon Source for the provision of the beamtime (RB2220620-1). The authors acknowledge the assistance provided by the Advanced Multiscale Materials for Key Enabling Technologies project, supported by the Ministry of Education, Youth, and Sports of the Czech Republic. Project No. CZ.02.01.01/00/22_008/0004558, Co-funded by the European Union. DZ has been supported by Charles University Research Centre program No. UNCE/24/SCI/010, and MG by the Grant Agency of Charles University: GAUK 267323.