2025
15.03.25
[Paper]
A new paper titled “Engineering hard ferrite composites by combining nanostructuring and Al3+ substitution: From nano to dense bulk magnets” was published (P. Maltoni et al., Acta Materialia 282, 120491, 2025). DOI: 10.1016/j.actamat.2024.120491
This study, has been devolpoed in collaboration with the Group of Prof. Roland Mathieu at Uppsala University . The study systematically investigated the morphological, structural, and magnetic properties of Al-substituted SrFe₁₂O₁₉ and SrFe₁₂O₁₉/CoFe₂O₄ nanocomposites, we identified key parameters governing their magnetic behavior.
Our results demonstrate that Al substitution in SFO significantly increases coercivity while preserving high saturation magnetization, offering an effective strategy for tuning magnetic properties without impurity phases. Furthermore, we explored two distinct synthesis routes for hard-soft nanocomposites: one based on preformed particles and the other on simultaneous co-synthesis of both phases. These approaches led to different cationic distributions and interface morphologies, revealing the critical role of synthetic control in optimizing super-exchange interactions. Monte Carlo simulations confirmed that enhancing interface exchange coupling improves remanent magnetization, aligning with experimental observations.
Additionally, we investigated the impact of spark plasma sintering (SPS) on the magnetic properties of the nanocomposites. SPS compaction improved particle alignment and strengthened exchange coupling, leading to increased remanent magnetization while maintaining distinct hard-soft phase interactions. Notably, the presence of both phases hindered mutual grain growth, preserving their intrinsic magnetic properties during sintering.
01.03.25
[Paper]
A new paper titled “Biphasic lithium iron oxide nanocomposites for enhancement in electromagnetic interference shielding properties ” was published (S. Ghosh et al., Journal of Alloys and Compounds 1010, 177017, 2025). DOI: 10.1016/j.jallcom.2024.177017.
This work has been supported by: "The Swedish Research Council (grant number 2021-03675). The Swedish Research Council (grant number 2023-05244). The Swedish Energy Agency (grant number P2020-90215). ÅForsk Foundation (grant number22-378).
The paper was jointly written with the group led by Prof. Tapati Sarkar at Uppsala University, Sweeden. This paper shows how by a careful tuning of the synthesis parameters, we can grow biphasic lithium iron oxide (ferrimagnetic α-LiFe5O8 and paramagnetic α-LiFeO2) nanocomposite with different relative fractions of the two phases. The variation of the phase fraction and the simultaneous growth of the two phases allow us to control the interfaces between the two phases as well as the physical properties of the nanocomposite, which have a direct effect on the EMI shielding performance. Improved dielectric and magnetic properties together with an increased number of interfaces in the sample with nearly equal amounts of the two phases results in the best performance. This work demonstrates the significant potential of using biphasic magnetic oxide nanocomposites with controllable interfaces and physical properties for EMI shielding, which can form the base for more complex triphasic systems in the future.
09.01.25
[Paper]
A new paper titled “Structural and magnetic properties of CoFe2O4 Nanoparticles in a α-Fe2O3 Matrix” was published (P. Maltoni et al., Journal of Physical Chemistry C 129, 591, 2025). DOI: 10.1021/acs.jpcc.4c05320
Supported by Swedish Energy Agency (Project No. 46561-1) and Swedish Research Council (VR); “Network 4 Energy Sustainable Transition-NEST” project (code PE0000021); European Commission PathFinder Open programme under grant agreement No. 101046909 (REMAP, REusable MAsk Patterning).
CoFe₂O₄ nanoparticles (~5 nm) were synthesized via the polyol method and subsequently embedded within an α-Fe₂O₃ matrix through a sol–gel process, forming a ferrimagnetic/antiferromagnetic nanocomposite. During synthesis, the CoFe₂O₄ nanoparticles aggregated into clusters within the antiferromagnetic α-Fe₂O₃ matrix, creating a complex interface between the two phases. Comprehensive characterization was carried out using SQUID magnetometry, Mössbauer spectrometry, X-ray powder diffraction (XRD), and transmission electron microscopy (TEM), providing detailed insights into both the structural and magnetic properties of the composite system.
A particular challenge addressed in the study was the synthesis of phase-pure α-Fe₂O₃ using sol–gel methods, as contamination with secondary phases often complicates the process. The researchers emphasized the critical importance of optimizing sintering conditions, such as temperature and duration, to achieve a pure hematite phase. The most striking discoveries were a significant enhancement in coercivity and the emergence of a magnetic bias, indicating superexchange coupling across the ferrimagnetic/antiferromagnetic interface. This coupling underscores the synergistic interaction between the phases, which is crucial for understanding the composite’s magnetism and potential applications in advanced magnetic devices.
This study sheds light on the interplay of structural and magnetic phenomena in ferrimagnetic/antiferromagnetic nanocomposites and underscores the importance of precision in chemical synthesis to tailor magnetic properties for specific applications.
