Article
Chemistry, Multidisciplinary
Georgiana Dolete, Cristina Chircov, Ludmila Motelica, Denisa Ficai, Ovidiu-Cristian Oprea, Marin Gheorghe, Anton Ficai, Ecaterina Andronescu
Summary: This article introduces a method for drug delivery and actuating mechanism using a magnetic film to meet the demanding use of controlled drug delivery systems. Magnetic alginate films were prepared in the laboratory, and the hypothesis that the magnetic field can trigger drug release from the films was validated by studying the release process.
Article
Chemistry, Physical
L. Wei, Y. W. Zhang, Y. S. Gong, Y. Hong, Z. G. Qiu, L. Z. Zhao, X. L. Liu, X. F. Zhang, D. Y. Chen, Z. G. Zheng, W. X. Xia, D. C. Zeng, N. M. Dempsey, J. P. Liu
Summary: This study systematically investigates the effects of RTP treatment on the magnetic anisotropy of SmCo-based films. The results show that RTP treatment can improve the magnetic properties and enhance the contrast of magnetic domains.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
Ke Wang, Zikun Xu, Xiaoyong Fu, Zhihong Lu, Rui Xiong
Summary: We investigated the magnetic and structural properties of sputtered thick Co2FeSi (CFS) alloy films. The X-ray diffraction measurements revealed that the CFS alloy film changed from amorphous to disordered A2 structures after annealing, resulting in a significant increase in saturation magnetization. The in-plane uniaxial magnetic anisotropy of the as-deposited films was found to be in the range of 103-104 erg/cm3, strongly dependent on the film thickness. After annealing, a fourfold cubic magnetic anisotropy was observed, and the structural ordering improved with increasing film thickness. The magnetic anisotropy showed a similar trend with the sputtering power, which can be explained by the equivalent annealing effect of high-power sputtering. Our results indicate that the magnetic anisotropy properties of CFS alloy films are strongly influenced by film thickness and structural ordering, which can be tuned by annealing temperature and sputtering power. These findings may have implications for the design of Co2FeSi-based spintronic devices.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Chemistry, Physical
Esther Frederick, Leah N. Appelhans, Frank W. DelRio, Kevin T. Strong, Sean Smith, Sara Dickens, Erika Vreeland
Summary: Metal-organic framework (MOF) thin films currently lack the mechanical stability needed for electronic device applications. This study developed a method to synthesize polyUiO-66(Zr) films and investigated their mechanical properties compared to UiO-66 thin films. The results showed that polyUiO-66 films have a lower modulus but similar hardness to UiO-66 films. Further development is needed to fully utilize the mechanical advantages of polyMOFs over MOFs. The continuous surface-supported polyUiO-66 thin films demonstrated in this work enable potential applications in sensors and devices.
Article
Materials Science, Multidisciplinary
Hao Li, Lu Wei, Yuan Hong, Yuanwei Zhang, Zhaoguo Qiu, Gang Wang, Lizhong Zhao, Xiaolian Liu, Xuefeng Zhang, Deyang Chen, Z. G. Zheng, Weixing Xia, Dechang Zeng, J. Ping Liu
Summary: This paper presents the preparation of SmCo-based thin films using magnetic field assisted magnetron sputtering and rapid thermal annealing. By decreasing in-plane magnetic anisotropy and increasing out-of-plane coercivity, the magnetic properties of the films are improved. Micromagnetic simulations confirm the significance of the proportion of magnetic moment direction in controlling magnetic anisotropy and coercivity.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Qian Li, Bo Wang, Qian He, Pu Yu, Long-Qing Chen, Sergei Kalinin, Jing-Feng Li
Summary: The mechanical switching of ferroelectric polarization in thick epitaxial films is demonstrated to be mediated by nanosized ferroelastic domains. This newly revealed mechanism, along with microstructure engineering, enhances the utility of mechanical switching and provides insight into competing polarization switching pathways in complex ferroelectric materials.
Article
Chemistry, Multidisciplinary
Robert Streubel, D. Simca Bouma, Frank Bruni, Xiaoqian Chen, Peter Ercius, Jim Ciston, Alpha T. N'Diaye, Sujoy Roy, Steve D. Kevan, Peter Fischer, Frances Hellman
Summary: Experimental evidence of 3D chiral spin textures, including helical spins and skyrmions with different chirality and topological charge, has been reported in amorphous Fe-Ge thick films. These results demonstrate that structurally and chemically disordered materials can resemble inversion symmetry broken systems with similar magnetic properties, moments, and states, providing greater flexibility in materials synthesis, voltage, and strain manipulation.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Physical
Malcolm Lockett, Viviana Sarmiento, Matthew Gonzalez, Seungbae Ahn, Jiaying Wang, Ping Liu, Oscar Vazquez-Mena
Summary: A novel ultrathin binderless anode based on stacked reduced multilayer graphene oxide and silicon nanowires was developed, showing a high specific capacity and capacity retention after multiple cycles. This innovative approach of producing well-ordered graphene multilayers by chemical vapor deposition offers promise for enhancing the energy density and stability of lithium-ion batteries.
ACS APPLIED ENERGY MATERIALS
(2021)
Article
Nanoscience & Nanotechnology
Elina Niinivaara, Johanna Desmaisons, Alain Dufresne, Julien Bras, Emily D. Cranston
Summary: The SIEBIMM method was used to quantify the Young's modulus of PVOH coatings reinforced with CNCs, showing a 13-fold increase in modulus due to factors such as CNC forming a percolated network, compatibility between CNCs and PVOH, and CNCs nucleating PVOH crystallites. Higher drying temperatures and lower relative humidity improved mechanical performance of CNC/PVOH coatings, increasing the modulus by 6 times compared to neat PVOH.
ACS APPLIED NANO MATERIALS
(2021)
Article
Materials Science, Ceramics
Jing Yan, Hanfei Zhu, Jun Ouyang, Isaku Kanno, Peng Yan, Yingying Wang, Kouta Onishi, Takumi Nishikado
Summary: Piezoelectric BiFeO3 films were successfully prepared on stainless steel foils and exhibited enhanced ferroelectric and dielectric properties. The optimized heterostructure achieved large piezoelectric coefficients for applications in actuators and energy harvesters.
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
(2022)
Article
Engineering, Electrical & Electronic
Frederico O. Keller, Richard Haettel, Thibaut Devillers, Nora M. Dempsey
Summary: In this study, standard micro-electro-mechanical systems (MEMS) fabrication techniques were used to batch fabricate out-of-plane textured Nd-Fe-B micro-magnets on Si substrates. The effects of substrate patterning and film thickness on the microstructures of the films were analyzed. The magnetic properties of the micro-magnets were comparable to sintered Nd-Fe-B bulk magnets. Scanning Hall probe microscopy was used to characterize the stray magnetic field patterns produced by the topographically patterned films.
IEEE TRANSACTIONS ON MAGNETICS
(2022)
Article
Chemistry, Multidisciplinary
Nadine Rassmann, Melina Weber, Roman E. J. Glass, Klaus Kreger, Nicolas Helfricht, Hans-Werner Schmidt, Georg Papastavrou
Summary: This study investigates the controlled electrochemical deposition of hydrogel films on ultraflat gold electrodes by studying the deposition of fibrillar networks. The resulting hydrogel film, formed through self-assembly of supramolecular fibrillar structures, was characterized in terms of its thickness. The film thickness was controlled by adjusting gelator concentration, applied potential, and gelation time. This research has potential applications in the field of biomedicine.
Article
Chemistry, Analytical
Denisa Ficai, Marin Gheorghe, Georgiana Dolete, Bogdan Mihailescu, Paul Svasta, Anton Ficai, Gabriel Constantinescu, Ecaterina Andronescu
Summary: Microelectromechanical systems (MEMS) have wide applications in various fields such as high tech, energy, medicine, and environment. Magnetic polymer films are extensively used in the development of microvalves and micropumps, which are critical components of MEMS. Based on literature survey, various polymers and magnetic micro and nanopowders have been identified, and their performances can be adjusted from simple valves and pumps to biomimetic devices depending on their nature, ratio, processing route, and device design.
Article
Biochemistry & Molecular Biology
Fei Song, Yu-Zhong Wang, Ze-Lian Zhang, Xiu Dong, Yu-Yao Zhao, Xiu-Li Wang
Summary: This article presents a method for developing flexible and elastic CNC composite films with visible structural colors and stretching-induced color change, resembling the skin of a chameleon, through co-assembly and polymerization strategy. The film can be designed as a smart skin for camouflage by adjusting the stretching.
Article
Physics, Multidisciplinary
Shuyao Chen, Yunfei Xie, Yucong Yang, Dong Gao, Donghua Liu, Lin Qin, Wei Yan, Bi Tan, Qiuli Chen, Tao Gong, En Li, Lei Bi, Tao Liu, Longjiang Deng
Summary: In this study, we addressed the challenge of achieving perpendicular magnetic anisotropy (PMA) in yttrium iron garnet (YIG) films thicker than 20 nm. By using substrates with moderate lattice mismatch, we successfully suppressed the excessive strain-induced stress release and achieved out-of-plane spontaneous magnetization even in YIG films as thick as 50 nm. Ferromagnetic resonance and spin pumping induced inverse spin Hall effect measurements confirmed the good spin transparency at the surface of our YIG films.
Article
Materials Science, Multidisciplinary
Yuxiao Jia, Yuye Wu, Yichen Xu, Ruixiao Zheng, Shiteng Zhao, Konstantin P. Skokov, Fernando Maccari, Alex Aubert, Oliver Gutfleisch, Jingmin Wang, Hui Wang, Jianxin Zou, Chengbao Jiang
Summary: In this study, a strategy to suppress twin formation in L1(0)-MnAl permanent magnets was proposed by reducing the grain and/or particle sizes below a critical size of D-t-300 nm. The results showed that the optimal coercivity can be achieved within the range of 50-200 nm, providing a pathway to achieve a twin-free microstructure with high texture degree in polymer-bonded or sintered magnets. These findings can be applied to other twin-containing permanent magnet compounds to increase their texture and maximal energy products.
Article
Materials Science, Multidisciplinary
M. Takhsha Ghahfarokhi, F. Casoli, C. Minnert, S. Bruns, E. Bruder, R. Cabassi, K. Durst, O. Gutfleisch, F. Albertini
Summary: Nanoindentation was applied to study the effect of localized plastic deformation on the martensitic transformation of epitaxial Ni-Mn-Ga films on a MgO substrate. The cooling and heating curves for the nanoindented areas were analyzed, showing a thermodynamically governed local increase of the martensitic transformation temperature as a function of applied loads. The observed effect is local and disappears beyond a certain distance from the pile-ups around the residual impressions.
Article
Materials Science, Multidisciplinary
Fernando Maccari, Alexander Zintler, Thomas Brede, Iliya A. Radulov, Konstantin P. Skokov, Leopoldo Molina-Luna, Oliver Gutfleisch
Summary: The ferromagnetic Mn-Al-C tau-phase has potential to be developed as a permanent magnet, but its metastable nature and decomposition to nonmagnetic phases negatively affect its magnetic properties. This study investigates a novel method using electric current-assisted annealing to obtain pure tau-phase samples. Results show that increasing electric current density reduces the required temperature for phase formation, with a maximum shift of 140 degrees C at 45 A mm(-2). Magnetic properties, however, are not affected by the electric current density. Microstructural analysis reveals the nucleation of the tau-phase at grain boundaries and the presence of twin boundaries during phase growth, resulting in similar extrinsic magnetic properties.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Lukas Schaefer, Konstantin Skokov, Fernando Maccari, Iliya Radulov, David Koch, Andrey Mazilkin, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Oliver Gutfleisch
Summary: A novel magnetic hardening mechanism is described, where modified Nd-Fe-B alloys undergo a solid-state phase transformation to increase coercivity. The presence of FeMo2B2 precipitates after thermal treatment refines the Nd2Fe14B grains and further enhances coercivity.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Halil Ibrahim Soezen, Semih Ener, Fernando Maccari, Bahar Fayyazi, Oliver Gutfleisch, Joerg Neugebauer, Tilmann Hickel
Summary: In this paper, an ab initio based approach was used to modify the stability of Laves phases in the Ce-Fe-Ti system by adding 3d and 4d elements, resulting in improved thermodynamic stability. The critical annealing temperature for the formation of Ce(Fe,X)11Ti was determined using accurate free-energy calculations and efficient screening technique. Promising transition metals such as Zn and Tc were predicted to enhance the stability of the hard-magnetic phase. Comparison with other alloy experiments highlighted the importance of additional phases and quaternary elements.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Engineering, Manufacturing
Olivier Tosoni, Elisa Borges Mendonca, Joni Reijonen, Atte Antikainen, Lukas Schaefer, Stefan Riegg, Oliver Gutfleisch
Summary: Additive manufacturing (AM) is a promising method for efficiently utilizing rare-earth elements in complex-shaped magnets. This study developed a close-to-industrial process to produce a narrow-distributed Nd-Fe-B powder and used it to build magnets using powder bed fusion with laser beam. After optimization and annealing, the magnets displayed excellent magnetic properties.
ADDITIVE MANUFACTURING
(2023)
Article
Materials Science, Multidisciplinary
Fernando Maccari, Tarini Prasad Mishra, Monica Keszler, Tobias Braun, Esmaeil Adabifiroozjaei, Iliya Radulov, Tianshu Jiang, Enrico Bruder, Olivier Guillon, Leopoldo Molina-Luna, Martin Bram, Oliver Gutfleisch
Summary: Flash spark plasma sintering (flash SPS) is an attractive method to obtain anisotropic Nd-Fe-B magnets with high magnetic performance by starting from melt-spun powders. The process promises electroplasticity and reduced tool wear, while maximizing magnetic properties through tailored microstructure. A parameter study reveals the importance of presintering conditions and preheating temperature on grain size and texture control. The best compromise between remanence and coercivity is achieved through a combination of specific parameters, resulting in a magnet with high energy product.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Mohammad Farhan Tanzim, Nuno Fortunato, Ilias Samathrakis, Ruiwen Xie, Ingo Opahle, Oliver Gutfleisch, Hongbin Zhang
Summary: In this study, the anomalous Hall conductivities (AHC) and anomalous Nernst conductivities (ANC) of thermodynamically stable ferro/ferri-magnetic all-d-metal regular Heusler compounds were evaluated through high-throughput first-principles calculations. It was found that several materials exhibited giant AHC and ANC values, such as cubic Re2TaMn with an AHC of 2011 S cm(-1) and tetragonal Pt2CrRh with an AHC of 1966 S cm(-1) and an ANC of 7.50 A m(-1)K(-1). The high AHC values were attributed to the presence of Weyl nodes or gapped nodal lines near the Fermi level. The correlations between these transport properties and the number of valence electrons were also thoroughly investigated, providing a practical guide for tailoring AHC and ANC through chemical doping for transverse thermoelectric applications.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Physics, Applied
Jianing Liu, Ruiwen Xie, Alex Aubert, Lukas Schaefer, Hongbin Zhang, Oliver Gutfleisch, Konstantin Skokov
Summary: The understanding of the coercivity mechanism in Nd-Fe-B permanent magnets relies on the analysis of magnetic properties of all phases present in the magnets. In this study, Nd6Fe13Cu single crystals were grown and their magnetic properties were studied. It was observed that Nd6Fe13Cu is antiferromagnetic below the Neel temperature and exhibits a spin-flop transition in a magnetic field. Atomistic spin dynamics simulation confirmed the change in antiferromagnetic coupling between Nd layers above and below the Cu layers, which causes the spin-flop transition. These findings suggest that the role of the Nd6Fe13Cu grain boundary phase in the coercivity enhancement of Nd-Fe-B-Cu magnets is more complex than previously thought.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Physical
Mario Schoenfeldt, Urban Rohrmann, Philipp Schreyer, Mahmudul Hasan, Konrad Opelt, Juergen Gassmann, Anke Weidenkaff, Oliver Gutfleisch
Summary: The effects of multiple recycling of scrap magnets from magnetic resonance tomography devices were investigated. The changes in different material properties were studied, including chemical composition, impurity content, particle size, magnetic properties, microstructure, and degree of alignment. The recycling process led to a decrease in texture, orientation, and magnetic properties, as well as an increase in impurities and particle size. The addition of Nd hydride improved the properties, with 4 wt.% Nd hydride fully restoring the density of the recycled magnets. The recycled magnets met the specification of primary magnets and outperformed them in terms of sustainability and production cost reduction.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Physics, Applied
Benedikt Beckmann, Tarek A. El-Melegy, David Koch, Ulf Wiedwald, Michael Farle, Fernando Maccari, Joshua Snyder, Konstantin P. Skokov, Michel W. Barsoum, Oliver Gutfleisch
Summary: Reactive single-step hot-pressing at high temperature and pressure can produce dense, near single-phase Fe-based MAB samples with favorable magnetocaloric properties. Ge and Ga doping can tailor the magnetic and magnetocaloric properties, increasing the Curie temperature and spontaneous magnetization. The hot-pressed samples show a second-order magnetic phase transition and have potential applications in low-cost and low-criticality magnetocaloric devices around room temperature.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Franziska Scheibel, Wei Liu, Lukas Pfeuffer, Navid Shayanfar, Andreas Taubel, Konstantin P. Skokov, Stefan Riegg, Yuye Wu, Oliver Gutfleisch
Summary: This study compares the properties of single-phase Ni-Mn-In alloys and two-phase Gd-doped Ni-Mn-In alloys and finds that the addition of Gd has little effect on the magnetocaloric performance, but greatly improves the mechanical stability by causing grain refinement.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Nuno M. Fortunato, Andreas Taubel, Alberto Marmodoro, Lukas Pfeuffer, Ingo Ophale, Hebert Ebert, Oliver Gutfleisch, Hongbin Zhang
Summary: Magnetic refrigeration is an efficient and eco-friendly alternative to traditional vapor-cooling, but its implementation relies on materials with tailored magnetic and structural properties. This study introduces a high-throughput computational workflow for designing magnetocaloric materials, using density functional theory calculations to screen potential candidates in the MM'X compound family (M/M' = metal, X = main group element). Out of 274 stable compositions, 46 magnetic compounds are found to stabilize in both austenite and martensite phases. By evaluating and comparing the structural phase transition and magnetic ordering temperatures, nine compounds with structural transitions are identified as potential candidates based on the concept of the Curie temperature window. Additionally, the use of doping to tailor magnetostructural coupling and isostructural substitution as a general approach to engineer magnetocaloric materials is suggested.
Article
Energy & Fuels
Wei Liu, Tino Gottschall, Franziska Scheibel, Eduard Bykov, Nuno Fortunato, Alex Aubert, Hongbin Zhang, Konstantin Skokov, Oliver Gutfleisch
Summary: Magnetocaloric hydrogen liquefaction has the potential to revolutionize the liquid hydrogen industry. Light rare-earth based materials offer a more sustainable alternative to heavy rare-earth compounds, with higher abundances and greater magnetocaloric effects in the required temperature range. By tuning the Curie temperature of light rare-earth alloys and mixing different rare-earth elements, a fully light rare-earth intermetallic series is developed, showcasing competitive maximum effects for hydrogen liquefaction compared to heavy rare-earth compounds like DyAl2.
JOURNAL OF PHYSICS-ENERGY
(2023)
Article
Chemistry, Physical
X. F. Liao, A. Aubert, F. Maccari, S. Riegg, S. Ener, E. Adabifiroozjaei, T. Jiang, L. Molina-Luna, K. Skokov, O. Gutfleisch
Summary: Grain boundaries play a crucial role in optimizing coercivity and densification in rare earth permanent magnets during sintering. This study focuses on grain boundary engineering of Nd-based ThMn12 magnets and their nitrides. By adjusting the Nd content and doping with Cu, the grain boundary phase properties can be controlled to enhance the sintering process and improve the relative density. However, the challenge lies in finding a suitable grain boundary for nitrides, as the existing grain boundary phase inhibits liquid-phase sintering.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
