Flexoresponses of Synthetic Antiferromagnetic Systems Hosting Skyrmions

Flexomagnetic Effect Enhanced Ferromagnetism and Magnetoelectrochemistry in Freestanding High-Entropy Alloy Films

“…The M ( H ) curves and the corresponding magnetization at 10 kOe of the Ni metal film (54.2 emu/g) and bulk CrMnFeCoNi HEA (1.0 emu/g) are given in Figure S6 (Supporting Information) as reference. Due to the short-range nature of magnetic exchange interactions, the changes in bond length and local symmetry under strain gradients are expected to change the magnetic properties of materials, − in agreement with our observed magnetic enhancement in wrinkled HEA film. Furthermore, the values of the exchange bias (EB) field at 2 K for wrinkled and flat HEA films are opposite in sign (Figure S7, Supporting Information), demonstrating the strain gradient-induced variation of the magnetic exchange interactions.…”

“…It is noteworthy that both strain and strain gradients are present in our wrinkled film, but the nonuniform strain gradients dominate (Figure S8, Supporting Information) based on the above discussions, and a maximum strain gradient of 25% per micron can be achieved (∇ε = dε/d t , ε and t are the magnitude of strain and film thickness, respectively) . This has also been reported in other inhomogeneously strained films, , which can induce the spin-reorientation following the atomic displacements because of the spin-exchange interaction in the antiferromagnet. − Thus, in our work, these large differences in magnetization of the BCC and FCC phases suggest that the partial structural phase transition caused by the inhomogeneous gradient term (∇ε) is responsible for the observed flexomagnetic coupling behavior.…”

“…Freestanding thin films are powerful platforms for multifunctional devices and manipulating properties via extreme strain (ε) and strain gradients (∇ε). − For example, in freestanding oxide thin films, extreme uniaxial strain exceeding 8% can be withstood before breaking, , and the strain gradients-induced tunable flexoelectricity has been observed, allowing the study of strain responses not achievable in substrate-supported thin films. Very recently, the coupling between magnetism and strain gradients, i.e., flexomagnetic effect, − has been demonstrated in experiments to induce a spontaneous magnetic moment of rippled GdPtSb alloy films at room temperature . Unlike piezomagnetism ( M ∝ ε) and magnetostriction ( M 2 ∝ ε) in thin films, which have been used to design sensors and actuators, − flexomagnetism ( M ∝ ∇ε) has attracted few attempts in practical applications, − in part due to the difficulties in fabricating and controlling the inhomogeneous strain gradients.…”

“…Very recently, the coupling between magnetism and strain gradients, i.e., flexomagnetic effect, − has been demonstrated in experiments to induce a spontaneous magnetic moment of rippled GdPtSb alloy films at room temperature . Unlike piezomagnetism ( M ∝ ε) and magnetostriction ( M 2 ∝ ε) in thin films, which have been used to design sensors and actuators, − flexomagnetism ( M ∝ ∇ε) has attracted few attempts in practical applications, − in part due to the difficulties in fabricating and controlling the inhomogeneous strain gradients. Moreover, the current research landscape of flexomagnetism is limited to very few experimental results of the emergent ferromagnetism in inhomogeneously strained antiferromagnetic materials, , so the impact of flexomagnetic coupling on phase transition and spin-reorientation of magnetic materials remains a vastly unexplored area to be investigated …”

“…Moreover, the current research landscape of flexomagnetism is limited to very few experimental results of the emergent ferromagnetism in inhomogeneously strained antiferromagnetic materials, 7,8 so the impact of flexomagnetic coupling on phase transition and spin-reorientation of magnetic materials remains a vastly unexplored area to be investigated. 9 Magnetism is also particularly attractive for tuning spinrelated electron transfer in electrochemistry, especially in magnetoelectrochemistry that couples the external magnetic field with electrocatalysts to control and understand the electrochemical reactions. 15−21 Unfortunately, numerous 3dtransition-metal materials are diamagnetic or paramagnetic at room temperature, which significantly impedes the application of the magnetic boosting strategy.…”