Flexible magnetoelectronics face a major challenge in maintaining functionality under mechanical strain. This research investigates how biaxial multicracking affects the magnetic properties of nanometric thin films, specifically by separating magnetoelastic from magnetostatic effects. Using a unique experimental platform, we show that in magnetostrictive Co films, the magnetic behavior is dominated by stress-induced magnetoelastic effects. In contrast, in non-magnetostrictive films, the magnetic changes only appear once multicracking begins, allowing us to demonstrate the magnetostatic contributions from fragmentation. Our findings reveal that the variation in the saturation field correlates directly with fragment shape. This work demonstrates that fragmentation is not just a failure mechanism but a controllable process whose magnetic effects can be understood and leveraged for designing next-generation flexible devices.

Controlling nanoscale heterogeneity in metallic glasses offers a promising route to tailor their mechanical behavior. In this work, we investigate (Zr34Cu66)100-xFex thin film metallic glasses (TFMGs) across a wide compositional range (x = 0 – 76 at.%) to reveal how immiscibility between Cu and Fe can lead to heterogeneity, thereby influencing their structure and mechanical properties. Guided by thermodynamic modeling, we show that (Zr34Cu66)100-xFex retains an amorphous structure up to 77.5 at.% Fe, enabling systematic investigation of a wide range of compositions within ZrCu-rich and Fe-rich regions. Ab initio molecular dynamics simulations reveal that Fe addition in the range of 17-29 at.% maximizes the population of highly stable icosahedral <0,0,12,0> motifs, thereby increasing hardness (H) from ∼7.9 up to ∼8.5 GPa, while further Fe increase leads to a reduction in H as a result of the weakening of atomic bonds. At 76 at.% Fe, atom probe tomography reveals the presence of Cu-rich amorphous clusters, accompanied by H decrement down to ∼7.6 GPa. Moreover, we show that nanoscale phase separation in the form of Cu-rich clusters controls the deformation mode, affecting the amplitude of strain rate serrations during nanoindentation, decreasing from ∼16 down to ∼5 for high Fe content, indicating a transition from localized to more homogeneous plastic flow. Overall, we demonstrate a simple approach to tailor local heterogeneities of TFMGs by introducing immiscible elemental constituents, successfully managing to control the mechanical behavior, which can be beneficial for advanced material applications.

Curvilinear magnetic nanostructures enable control of magnetization dynamics through geometry-induced anisotropy and chiral interactions, as well as magnetic field modulation. In this work, we report a curvilinear magnonic crystal based on large-area square arrays of truncated nanospikes fabricated by conformal coating of 3D hierarchical templates with permalloy thin films. Brillouin light scattering spectroscopy reveals an anisotropic band structure with multiple dispersive and folded Bloch-type dispersive spin-wave modes as well as nondispersive modes exhibiting direction-dependent frequency shifts and intensity asymmetries along lattice principal axes. Finite element micromagnetic simulations indicate that curvature-induced variations of the demagnetizing field govern the magnonic response, enabling the identification of modes propagating in nanochannels and others localized on nanospike apexes or along the ridges connecting adjacent nanospikes. The combination of geometric curvature and optical probing asymmetry produces directional dependence of magnonic bands, establishing 3D hierarchical templates as a versatile platform for curvature-engineered magnonics.

Prospective spintronic memory and logic devices will benefit from the negligible stray field and ultrafast magnetic dynamics inherent to antiferromagnets [1]. However, realizing isothermal, nonvolatile, and deterministic switching of antiferromagnetic states remains a key challenge [2, 3]. Here, we propose a piezomagnetic writing scheme in triangular Mn3Ir-based memory cells, with readout achieved via the exchange bias effect. Our approach enables deterministic and nonvolatile switching of the antiferromagnetic states, which exhibit exceptional robustness against external perturbations. The switching mechanism is ascribed to piezomagnetic effect of Mn3Ir combined with the interfacial Dzyaloshinskii-Moriya interaction at the antiferromagnet-ferromagnet interface. This scheme overcomes the speed limitations imposed by conventional isothermal methods based on isothermal crystallization mechanism [4]. Our findings highlight the potential of piezomagnetic effects in designing advanced spintronic devices, providing an efficient pathway for manipulating antiferromagnetic states and developing energy-efficient memory technology.

We report a strategy to tailor the magnetoelastic response of flexible ferromagnetic thin films by engineering their mechanical fragmentation through material selection and multilayer design. Using in situ magneto-optical Kerr effect (MOKE) magnetometry combined with uniaxial tensile testing and optical imaging, we explore how ductile and brittle behaviors influence the evolution of magnetic anisotropy and coercivity under strain. Comparative studies of Co monolayers, Co/W, Co/Au bilayers, and Ni films reveal that the nature of the underlayer and the film thickness critically determine the fragmentation pattern, the onset of buckling, and the resulting magnetoelastic field. We show that in brittle systems, abrupt stress redistributions caused by multicracking and buckling lead to sharp, nonreversible changes in magnetic properties, while ductile systems exhibit gradual, tunable responses due to progressive plastic deformation. These results highlight a design framework for controlling magneto-mechanical functionality in flexible magnetic systems, offering pathways for reconfigurable magnetic devices and strain-adaptive electronics.

The magnetic behaviour of a material can be altered by stresses and defects. As in polycrystalline thin films stress can be measured in situ during a deformation test using X-ray diffraction, we have developed an experimental setup that combines multiple techniques to measure stresses and analyse both mechanical and magnetic behaviours. The capabilities of our experimental setup are presented via the results obtained on a ferromagnetic Ni60Fe40 thin film (20 nm thick) deposited on a polymeric substrate. In order to cover the elastic and the cracking regimes, the films have been subjected to controlled biaxial tensile tests, i.e. two deformation paths, one to create cracks parallel to the applied magnetic field (H), and a second to create cracks perpendicular to H. The evolutions of the hysteresis loops, the measured stress, the damage and the cracking are discussed as functions of the applied deformation. In particular, there is evidence that the measured stress and magnetisation cycles are related by magneto-elastic effects, while the orientation of the cracks relative to the direction of the applied magnetic field shows a magnetic in-plane anisotropy. The stresses distribution in the ferromagnetic Ni60Fe40 thin film is clearly the main factor affecting magnetic behaviour, while crack creation and propagation have a negligible effect.

We explore the magnetic properties of a thin Co film deposited on Kapton® substrates using the magneto-optical Kerr effect in a longitudinal configuration. We developed a magnetometer integrated with a tensile testing machine to investigate magnetization reversal phenomena under applied strain. The tensile machine, custom-designed to fit the experimental constraints, applies uniaxial stress to the samples, facilitating the study of magnetoelastic effects. Calibration using digital image correlation ensures accurate strain measurements. Our findings demonstrate that the application of strain significantly influences the magnetization curves, highlighting the emergence of anisotropies and changes in coercive and saturation fields.

The magnetization dynamics of square arrays of circular antidots fabricated on Si(001) substrates using deep ultraviolet lithography with a 248 nm exposing wavelength have been studied. The effects of thickness (40 nm and 80 nm) and the in-plane direction of the applied magnetic field on the magnetostatic mode energies were investigated through ferromagnetic resonance experiments and micromagnetic simulations for both thicknesses. The experimental results and the simulations allowed the determination of nature of the magnetostatic modes nature measured at angles of 0 degrees and 45 degrees between the applied magnetic field and the axis of the square array. Notably, in this geometry, the main modes do not disapear when the sample is rotated; instead, the localization of the modes follow the rotation of the applied field, with a variation in measured intensity directly related to the surface area occupied by the localized mode.

Elastically strained ferromagnetic objects have been studied by coupled micromagnetic-mechanical numerical simulations. Both temporal evolution of the magnetization and modal frequency analysis of ferromagnetic thin films and arrays of nanostructures are presented. For this purpose, we have numerically coupled the micromagnetic equations (including magnetoelastic effects) to the ones of solid mechanics by including periodic boundary conditions. Our approach has been evaluated first on an elastically strained thin film and validated by performing in situ ferromagnetic resonance experiments. We have undertaken simulations on nanostructured arrays (modulated arrays of nanowires) and show that the heterogeneity of the strain fields and magnetic mode profiles of those strained nanostructures induce significative disparities in the magnetic mode energies, allowing applications to be foreseen where one could control in a differentiated way the spin-wave energies as a function of the applied elastic strains.

The influence of multi-cracking on the magnetic response of more (Co) or less (Ni78Fe22) magnetostrictive ferromagnetic nanofilms on flexible substrates has been studied by combining tensile tests with in situ magneto-optical Kerr effect magnetometry measurements, up to large strain (20%). The results show that the variations of the magnetic features are more significant in the elastic domain (before cracking), while they are slightly affected in the multi-cracking regime, linked to the fact that the stresses evolve relatively little in this regime. This results in a lesser modification of the magnetization curves of Ni78Fe22, which also means weak magnetostatic (dipolar) effects despite a very high crack density. This is very promising for the applicability of magnetic films in highly curved or stretched systems, especially using weakly magnetostrictive materials.

A unique deposition approach combining atomic layer deposition (ALD) and magnetron sputtering was used to fabricate a series of thin film multilayer structures of Al (50 nm) and Al2O3 (ALD, 2.4-9.4 nm) on flexible polymer substrates without breaking vacuum. The multilayers together with 50 nm and 150 nm Al reference films were analyzed by cross-sectional TEM analysis and experimentally strained in biaxial tension to investigate their deformation behavior. Al film stresses and peak widths, measured in situ with Synchrotron X-ray diffraction, are in good agreement with post-mortem surface SEM and through-thickness FIB analysis of the multilayers. It was revealed that brittle cracking of the multilayer can be avoided, and that the lateral and through-thickness crack resistance improve as a function of decreasing oxide layer thickness. An attempt to model the full biaxial yield surface of the multilayers, which remains experimentally challenging, appears to be valid up to 2.4 nm oxide thickness. Model predictions are further compared to compression data, obtained from the unloading segments of the tensile tests. Describing the mechanical behaviour under multiaxial stress conditions is of utmost importance for a diverse understanding of these multilayers across a variety of potential carrier systems and loading cases.& COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

In a recent paper (G. Muscas et al.),(1) the magnetomechanical behavior of cobalt (Co) magnetic nanowire arrays on a polymeric substrate (polyethylene naphthalate (PEN)) under bending was measured by magneto-optical Kerr effect (MOKE) magnetometry in situ. The authors showed that the magnetomechanical effects were very small and assigned this result to a low effective magnetostriction coefficient due to the nanostructuring. In this comment, we show by numerical calculations that it is the ongoing/current stress distribution within the system that generates this effect. Indeed, the nanostructures being very rigid with respect to the compliant substrate, the strains are mainly concentrated in the substrate and less than 3% of the macroscopic stress is transmitted to the nanostructures.

In the comment to our paper, D. Faurie et al. have carried out simulations on Co-nanowires subjected to tensile stress perpendicular to the length of the nanowires. According to their simulation, the low effective magnetostriction constant of the Co nanowires results from a very low transfer of stress. They suggest that a higher transfer of stress would be obtained if the wires are bent along the length of the nanowires. Here we compare the result of magneto-optical experiments conducted by bending the nanowires both along and perpendicular to their long axis. The obtained effective magnetostriction of the Co-nanowires is, within the experimental resolution, independent of the bending direction.

The influence of the strain ratio (equibiaxial or uniaxial) and the strain path (equibiaxial or sequenced uniaxial) on the cracking of metallic thin films is studied. We used 20, 100 and 600 nm Nickel films deposited onto flexible substrates, analysed with in-situ X-ray diffraction and digital image correlation, and post-mortem optical microscopy. It is shown that the thickness and the loading ratio effects are interweaved. In particular, 600 nm films show a small (1.9%) von Mises fracture strain and straight cracks when strained equibiaxially, but a larger (2.7%) fracture strain and more tortuous cracks when strained uniaxially. On the contrary, 20 and 100 nm thin films show different von Mises ultimate tensile strengths, though their von Mises fracture strain and theirs cracks tortuosity hardly depend on the test.

The realization of mechanically compliant spintronic elements relies on magnetic thin films prepared on flexible polymeric foils. Due to the strong difference in the mechanical properties of the magnetic thin film and the polymeric support, strong effects of heterogeneous strain emerge, which govern the magnetic response of the magnetic nanomembrane. Herein, the effect of the heterogeneous strain in a prototypical magnetic nanomembrane of Ni on the application‐relevant polyimide foil is studied. The distribution of the magnetoelastic field in the case of the heterogeneous strain is taken into account and compared with the case of the free‐standing Ni thin film. It is shown that the reversal process is strongly influenced by the heterogeneity at the early stages. Indeed, the reversal is characterized by two modes in the heterogeneous case, due to the strain localization in the nanomembrane, whereas the homogeneous case is characterized by a single mode. In contrast, the strain heterogeneity does not change significantly the postreversal oscillations as well as the equilibrium configuration for a given mean strain. These results are strongly relevant for a broad magnetism community working in the field of curvilinear magnetism, shapeable magnetoelectronics, and straintronics.

This paper provides a topical review of work on systems based on magnetic nanostructured thin films on polymer substrates. This topic has indeed experienced a significant growth in the last ten years. Several studies show a strong potential of these systems for a number of applications requiring functionalities on non-planar surfaces. However, the deformations necessary for this type of applications are likely to modify their magnetic properties, and the relationships between strain fields, potential damages and functional properties must be well understood. This review focuses both on the development of techniques dedicated to this research, on the synthesis of the experimental results obtained over the last ten years and on the perspectives related to stretchable or flexible magnetoelectric systems. In particular, the article focuses on the links between magnetic behavior and the strain field developing during the whole history of these systems (elaboration, reversible and irreversible loading).

This paper presents the prospects for periodic magnetic nanostructures in the form of magnonic crystals on polymer substrates. Indeed, arrays of magnetic nanostructures on flexible substrates are promising for microwave applications in the GHz frequency range. In particular, the mastery of the potentially coupled physical properties (magnetic and mechanical) allows one to consider devices for microelectronics in general, combining the microwave properties of spin waves with the lightness and conformability of polymer substrates. However, there are still scientific hurdles to be overcome, particularly with regard to the reliability of these systems, which is the focus of this review. Subsequently, we propose a general state of the art, a summary of the precursor works, and a general strategy for the optimization of these systems and their future possibilities.

Broadband ferromagnetic resonance (FMR) has been used to investigate the dependence of the magnetic damping enhancement in CoFeB/Pd bilayer systems due to spin pumping. This study has been realized on a series of samples characterized by a fixed CoFeB thickness of 6 nm while the Pd thickness varies from 2 to 30 nm (tPd = 2, 4, 6, 8, 12, 20 and 30 nm). This series has been simultaneoulsy deposited on two different substrates: a rigid one (Si) and a flexible one (Kapton). The results obtained from the analysis of the FMR measurements reveal show an exponential behaviour of the Gilbert damping as function of the Pd thickness in both kind of substrate. The experimental data was analysed using an anaytical model for spin pumping [1,2], which includes the effective spin mixing conductance of the CoFeB/Pd interface and the spin-diffusion length. The estimated values are around 6 nm−2 for both substrates whereas the diffusion length differs significantly between the two substrates (5.22 nm for Si sunbstrate and 1.11 nm for Kapton substrate). The obtained results demonstrate the efficiency of the possibility of tuning the Gilbert damping constant by a judicial choice of the nonmagnetic film, depending on the desired application. References: [1] Foros J, Woltersdorf G, Heinrich B and Brataas A 2005 J Appl. Phys. 97 10A714 [2] Shaw J M, Nembach H T and Silva T J 2012 Phys. Rev. B 85 054412

The control of localized magnetic modes has been obtained in Ni60Fe40 square lattice (600 nm) antidot arrays. This has been performed by tailoring the magnetoelastic field at the scale of the antidot primitive cell. The corresponding heterogeneous strain field distributions have been generated by a PZT substrate and enhanced by the incorporation of a supporting compliant layer. It has been highlighted by a differentiated variation of magnetic energy directly due to the local magnetoelastic field felt by each magnetic mode, probed by ferromagnetic resonance spectroscopy. A modeling, involving micromagnetic simulations (to locate the magnetic modes), full-field simulations (to evaluate the strain field distributions), and an analytical model generally dedicated to continuous film that we have extended to those magnetic modes, shows a good agreement with the experimental data. This approach is very promising to develop multichannel systems with simultaneous and differentiated controlled frequencies in magnetic devices.

La2/3Sr1/3MnO3 (LSMO) thin films of various thicknesses (6, 8, 10, 20, and 30 nm), capped by 7 nm‐thick Pt layer, are grown by pulsed laser deposition on SrTiO3 (001) substrates. X‐ray diffraction revealed that LSMO films are (001) oriented. Vibrating sample magnetometer is used to determine the magnetization at saturation and the magnetic dead layer thickness. This latter is around 3.4 nm, significantly thicker compared with the one induced at interfaces of Pt with ferromagnetic transition metals. Microstrip line ferromagnetic resonance (MS‐FMR) is used to extract the gyromagnetic ratio, which is found to increase with LSMO thickness. MS‐FMR revealed that the in‐plane magnetic anisotropy is dominated by a uniaxial contribution for the Pt capped film, whereas the noncapped 10 nm‐thick LSMO layer shows a fourfold anisotropy. Furthermore, the thickness dependence of the effective magnetization reveals the existence of a second‐order perpendicular anisotropy term, which is thickness‐dependent, and of a weak uniaxial interface anisotropy. The Gilbert damping coefficient is found to vary linearly with the inverse of the effective LSMO thickness due to spin pumping leading to relatively low spin mixing conductance of LSMO/Pt interface.