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Strain effect on magnetic anisotropy of Ta (2 nm)/NiFe (5 nm)/Ta (2 nm) films. a), b) Schematic of strain application and sample measurements by a magneto–optical Kerr microscope: a) ε ⊥ HI; b) ε // HI. c), d) Variations of the Kerr signal at remnant magnetization state with θ: c) ε ⊥ HI; d) ε // HI. The arrows in the panel (c) represent the maximum Kerr signal. e–j) Typical Kerr curves at θ = 80°: e–g) ε ⊥ HI; h–j) ε // HI.
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Manipulation of the antiferromagnetic moment in antiferromagnets (AFMs) is a crucial issue for developing AFM‐based spintronic devices. Lattice strain is an effective strategy to modulate the antiferromagnetic moment and is traditionally based on a direct crystalline tailoring of AFMs. A novel method for strain tuning the antiferromagnetic moment b...
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Citations
... 24 In addition to controls by ultrahigh magnetic fields in conventional antiferromagnets 25,26 and electric fields in antiferromagnets/substrates with magnetoelectric interactions, 27,28 strain has become one of the most interesting approaches to tune magnetic properties of antiferromagnets. [29][30][31][32][33][34][35][36] Tang et al. 29 increased the exchange bias field from 140 to 250 Oe by improving the crystalline structure and morphological uniformity in CoFe/IrMn bilayers by reducing the sputtering pressure. Furthermore, a distinct enhancement of $900% in the exchange bias field from 20 to 200 Oe was achieved in (FeCo/IrMn) 3 /Ta multilayers grown on top of a flexible polyimide substrate with a pure mechanical compressive strain of -6.26%. ...
... 32 Utilizing thermally driven inverse martensitic phase transformation of a shape memory alloy substrate, not only a twirling of the N eel vector but also a maximal variation of 350% in the exchange bias field was observed in NiFe/FeMn bilayers. 33 Previously, our group and coauthors studied the exchange bias behavior in Ni-Mn-Sn Heusler alloy films under the application of both tensile and compressive strains and found that the exchange bias field was strongly strengthened as well, and meanwhile, the exchange bias blocking temperature was significantly increased by 10 K. 34 Finally, the realizations of exchange bias control by strain through alternating stacking sequence of heterostructures 35 and substrate layer thickness 36 have been reported. ...
We propose a numerical method, where first-principles calculations are combined with modified Monte Carlo simulations, and study the Néel temperature of antiferromagnetic IrMn and exchange bias effect in antiferromagnet/ferromagnet IrMn/CoFeB bilayers manipulated by the applications of tensile and compressive strains. The results show that both tensile and compressive strains linearly change the magnetic moment of Mn and the magnetocrystalline anisotropy of IrMn, and meanwhile, the uniaxially easy-axis directions under tensile and compressive strains are perpendicular. The strain-triggered increase in antiferromagnetic exchange coupling between Mn–Mn pairs is revealed and induces an up to 1.5 times enhancement of the Néel temperature of IrMn. Furthermore, the spontaneous and conventional exchange bias effects can be both observed under large tensile strains, also sensitive to the cooling field, and strongly enhanced roughly by 800% under 8 T in the application of 1.5% strain, which can be interpreted by the strain-induced high magnetocrystalline anisotropies. Thus, the tensile strains are better for controlling and optimizing the Néel temperature of IrMn and further exchange bias properties in IrMn-based heterostructures. This work establishes the correlations between microscopically and macroscopically magnetic responses to strain, indicating that strain can be an intriguing means of extrinsic manipulation of exchange bias, which is of importance for spintronic device applications.
... Therefore, systematic investigations based on the thin film deposition parameters such as growth rate, base pressure, and annealing temperature have been of current interest [20,27]. Recently, external strain-induced control of the exchange bias effect revealed the tunable functionalities in NiFe/ FeMn exchange bias multilayers [28]. Past investigations are mostly focused on the hysteresis properties of magnetization upon magnetic field reversals. ...
... In previous studies, the methods for manipulating EB mainly include stress [19,20], voltage [21], field cool [11,22], large pulsed magnetic field [23], all-optical helicity [24], and the spin-orbit torque (SOT) effect produced by spin current in recent years [25][26][27]. Traditional methods have certain limitations, for example, the power consumption of the pulsed magnetic field to control the EB is very large, and the premise of the SOT to manipulate the EB is that the sample has strong spin-orbit coupling or a large spin Hall angle. ...
Exchange bias has extremely important applications in spintronics, researchers have proposed various means to manipulate it. This work realizes the regulation of the exchange bias field in Co/IrMn films sputtered on LiNbO3 substrate by the surface acoustic wave. The experimental results show that in the out-of-plane and in-plane exchange bias of Co/IrMn films, both the coercivity and the exchange bias field decrease with the increase of the surface acoustic wave power. The dynamic strain field provided by the surface acoustic wave transfer to the magnetic films changes the arrangement of the magnetic moments in the Co layer and IrMn layer, the rearrangement of magnetic moments leads to a reduction in the exchange bias field. Our experiments provide an approach to manipulate the exchange bias field, opening a potential avenue for manipulating antiferromagnetic moments in the future.
... On the one hand, the SMPs are considered to have a slower recovery speed than that of shape memory alloys (SMAs). However, the controllable strain of SMAs is only 8% [33], which is much smaller than that of SMPs (up to 800%) [34], and the deformation capacity of SMAs can only be improved by restricted structural design [35]. The SMA actuator is wire [36] with a limited diameter and size such as a spring-like structure [37,38]. ...
Shape-memory polymers (SMPs) have gradually emerged in the mechanism and biomedical fields and facilitate the upgrading of industrial mechanisms and the breakthrough of technical bottlenecks. However, most of the SMPs are infeasible in harsh environments, such as aerospace, due to the low glass transition temperature. There are still some works that remain in creating truly portable or non-contacting actuators that can match the performances and functions of traditional metal structures. Polyether-ether-ketone (PEEK) with a high glass transition temperature of 143 °C is endowed with outstanding high-temperature resistance and radiation-resistant properties and shape memory behavior. Thus, we explore the shape-memory properties and actuation performances of high-temperature PEEK in bending behaviors. The shape-recovery ratio, actuation speed and force under different programming conditions and structure parameters are summarized to complete the actuation capacities. Meanwhile, a metallic ball transported by shape-memory PEEK and deployed drag sail with thermo-responsive composite joints were shown to verify the potential in aerospace.
... 13 Additionally, x-ray magnetic linear dichroism (XMLD) on Mn 2 Au showed a 0.1% tensile strain produced a N eel vector reorientation energetically equivalent to an applied magnetic field of 70 T. 25 Similar XMLD studies on a Fe 50 Mn 50 /Ni 50 Fe 50 exchange-spring demonstrated an 80 in-plane (IP) N eel vector reorientation with a À1.3% strain applied from a NiTi substrate. 26 While all these results provide new and important information, the relationship between mechanical strains and reorienting the N eel vector across a variety of AFM materials (including FeMn) requires further examination. ...
... There has been a previous report on equimolar FeMn thin films demonstrating magnetostrictive properties (i.e., changes in the N eel vector orientation with strains) using compression in an exchange spring FeMn/NiFe laminate. 26 Additionally, there have been several reports on bulk FeMn with giant magnetostriction reporting values from 160 to 2000 ppm. [20][21][22] However, while bulk FeMn samples have provided reports of measured magnetostriction values, the magnitude of magnetostriction (k s ) in thin film AFMs, such as FeMn, has not been published. ...
The relationship between stresses and the orientation of the Néel vector were studied by varying the residual stresses in magnetron sputtered FeMn thin films by adjusting Argon working pressures. Quasistatic magnetization and AC susceptibility measurements reveal that the FeMn film with compressive stress (−27 MPa/−0.015% strain) possesses an out-of-plane Néel vector orientation with a 44 kOe spin-flop field, as contrasted to the FeMn film with tensile stress (25 MPa/0.014% strain) showing an in-plane orientation with a 34 kOe spin-flop field. An energy formulation for the films estimates a magnetostriction value of 109 ppm following an effective anisotropy of −8 kJ/m ³ . The film with the larger residual stress (77 MPa/0.043% strain) displayed a strain-induced phase transition from γ-FeMn to α-FeMn. These results show the dependency of the Néel vector on the stress state indicative of relatively large magnetostriction.
... This effect was explained by the appearance of the AFM domain walls parallel to the interface. In addition, the observed features can be useful for developing novel methods [44] for tuning the exchange spring in the AFM. ...
Magnetization reversal processes in the NiFe/FeMn exchange biased structures with various antiferromagnetic layer thicknesses (0–50 nm) and glass substrate temperatures (17–600 °C) during deposition were investigated in detail. Magnetic measurements were performed in the temperature range from 80 K up to 300 K. Hysteresis loop asymmetry was found at temperatures lower than 150 K for the samples with an antiferromagnetic layer thickness of more than 10 nm. The average grain size of FeMn was found to increase with the AFM layer increase, and to decrease with the substrate temperature increase. Hysteresis loop asymmetry was explained in terms of the exchange spring model in the antiferromagnetic layer.
... [1][2][3] Nowadays, mechanical strain tuning of magnetic propeties is one of the most widely used research methods with mature thin-film preparation technology, promoting the further development of flexible devices. Various flexible substrates (e.g., metal foils, [4] graphites, [5] polymers materials [6] and shape memory alloys [7,8]) have been used in diverse electronic devices. However, to meet the demands for highquality thin film preparation, some flaws of metal foils and polymers materials, such as poor textures, rough surface and instability toward heat, make them difficult to be used to directly deposit thin films. ...
Mechanical strain tuning of magnetic properties is crucial for developing flexible electronic and spintronic devices. Here, (111)-oriented CuFe2O4 (CuFO) thin films are epitaxially grown on flexible mica substrates, and the influence of the mechanical strain on magnetic properties is investigated by altering the curvature of the CuFO/mica structures. Both the in-plane and out-of-plane saturation magnetic moments increase monotonously with the decrease of bending radius, which can be ascribed to the mechanical strain-induced Jahn-Teller distortion and much easier neighboring ferromagnetic domain switching in the CuFO films. Particularly, the residual magnetization can be dramatically enhanced by mechanical strain with a large gauge factor of 321.25, demonstrating effective strain tuning of magnetism. Moreover, the CuFO/mica structures exhibit strain tunable parallel magnetic anisotropy and excellent mechanical antifatigue properties. This work implies a great potential for promissing applications in flexible spintronics and electronics.
... The strong coupling of mechanical strain to various internal degrees of freedom involving charges, photons, spins, etc., also enables the design and implementation of device technologies with novel functionalities, such as stretchable electronics/optoelectronics [18][19][20][21], quantum straintronics [22][23][24][25], electromechanical sensors [26][27][28], strain-engineered piezotronics [29][30][31][32], and mechanically enhanced catalysis [33][34][35]. Strain engineering in 1D semiconductors such as silicon [6,7,36] and ZnO [29,31,37] nanowires has been explored theoretically [38][39][40][41][42][43][44] and experimentally [7,36,45,46] as an effective approach to rationally engineer the crystal structure, semiconductor properties, and device functions of the related materials [47][48][49][50][51][52][53][54]. ...
The low-dimensional, highly anisotropic geometries, and superior mechanical properties of one-dimensional (1D) nanomaterials allow the exquisite strain engineering with a broad tunability inaccessible to bulk or thin-film materials. Such capability enables unprecedented possibilities for probing intriguing physics and materials science in the 1D limit. Among the techniques for introducing controlled strains in 1D materials, nanoimprinting with embossed substrates attracts increased attention due to its capability to parallelly form nanomaterials into wrinkled structures with controlled periodicities, amplitudes, orientations at large scale with nanoscale resolutions. Here, we systematically investigated the strain-engineered anisotropic optical properties in Te nanowires through introducing a controlled strain field using a resist-free thermally assisted nanoimprinting process. The magnitude of induced strains can be tuned by adjusting the imprinting pressure, the nanowire diameter, and the patterns on the substrates. The observed Raman spectra from the chiral-chain lattice of 1D Te reveal the strong lattice vibration response under the strain. Our results suggest the potential of 1D Te as a promising candidate for flexible electronics, deformable optoelectronics, and wearable sensors. The experimental platform can also enable the exquisite mechanical control in other nanomaterials using substrate-induced, on-demand, and controlled strains.
... Controlling the Néel vector without electrical current is promising for ultra low power applications, since it has been predicted that magnetization reversal can be achieved with aJ level energy consumption 10 . Electric field control of the magnetic properties of AFMs can be realized indirectly through the mechanism of mechanical strain created from a piezoelectric substrate [11][12][13][14] or a combination of strain plus exchange spring 15 . It can also be realized directly through the mechanism of voltage controlled magnetic anisotropy (VCMA). ...
CrSb is a layered antiferromagnet (AFM) with perpendicular magnetic anisotropy, a high Neel temperature, and large spin-orbit coupling (SOC), which makes it interesting for AFM spintronic applications. To elucidate the various mechanisms of Neel vector control, the effects of strain, band filling, and electric field on the magnetic anisotropy energy (MAE) of bulk and thin-film CrSb are determined and analysed using density functional theory. The MAE of the bulk crystal is large (1.2 meV per unit cell). Truncation of the bulk crystal to a thin film consisting of an integer number of unit cells breaks inversion symmetry, creates a large charge dipole and average electric field across the film, and breaks spin degeneracy, such that the thin film becomes a ferrimagnet. The MAE is reduced, and its sign can be switched with realistic strain. The large SOC gives rise to an intrinsic voltage controlled magnetic anisotropy (VCMA), with a VCMA coefficient similar to that of FeRh/MgO and other heavy-metal/ferromagnetic/MgO structures.
Emerging fields, such as wearable electronics, digital healthcare, the Internet of Things, and humanoid robots, highlight the need for flexible devices capable of recording signals on curved surfaces and soft objects. In particular, flexible magnetosensitive devices garner significant attention owing to their ability to combine the advantages of flexible electronics and magnetoelectronic devices, such as reshaping capability, conformability, contactless sensing, and navigation capability. Several key challenges must be addressed to develop well‐functional flexible magnetic devices. These include determining how to make magnetic materials flexible and even elastic, understanding how the physical properties of magnetic films change under external strain and stress, and designing and constructing flexible magnetosensitive devices. In recent years, significant progress is made in addressing these challenges. This study aims to provide a timely and comprehensive overview of the most recent developments in flexible magnetosensitive devices. This includes discussions on the fabrications and mechanical regulations of flexible magnetic materials, the principles and performances of flexible magnetic sensors, and their applications for wearable electronics. In addition, future development trends and challenges in this field are discussed.
