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Abstract Layered 3d‐orbital ferromagnet is an ideal research platform to experimentally achieve intrinsic 2D ferromagnetism and theoretically study the quantum nature of magnetic exchange interactions therein. A variety of magnetic phases can emerge from the strongly correlated feature of 3d‐orbital electrons, in which their exchange interactions can be effectively modulated by various kinds of external stimuli. Therefore, controlling the emergent magnetic phenomena of layered 3d‐orbital ferromagnets is significant in both fundamental science and practical applications. Considering the roles of magnetic exchange interactions, this review summarizes recent progress in controlling the emergent magnetic properties of layered 3d‐orbital ferromagnets by systematically introducing modulation methods, underlying mechanisms, and device applications. The existing challenges and future prospects for this research field are also outlined, shedding light on finding optimized magnetic materials, exploring powerful modulation techniques, and designing multifunctional new concept devices.

Magnetic field sensors based on the giant magnetoresistance (GMR) effect have a number of practical current and future applications. We report on a modeling of the magnetoresistive response of moving spin-valve (SV) GMR sensors combined in certain cluster networks to an inhomogeneous magnetic field of a label. We predicted a large variety of sensor responses dependent on the number of sensors in the cluster, their types of interconnections, the orientation of the cluster, and the trajectory of sensor motion relative to the label. The model included a specific shape of the label, producing an inhomogeneous magnetic field. The results can be used for the optimal design of positioning devices.

Periodic systems of magnetic nanoparticles are now of interest as they support GHz spin waves. Their equilibrium configurations, switchable with the external magnetic field, are crucial for such applications. We study infinite and finite chains of particles of two shapes (i) ellipsoidal and (ii) rectangular stripes with long axes perpendicular to the chain axis. A variable magnetic field is applied parallel to the long axes. Micromagnetic simulations are compared with the corresponding discrete spin models (Stoner-Wohlfarth model, S-W). An antiferromagnetic configuration is the ground state for all the systems at vanishing field but a ferromagnetic configuration occurs when the field is strong enough. The switching of the infinite chains to the reversed ferromagnetic configuration proceeds directly for the ellipsoids and by an intermediate configuration, in which the magnetization within the particle is non-uniform, in the case of the stripes. The non-uniform configurations are well represented by tilted states in S-W model. Important differences are found in the finite analogs: the switching of ellipsoids becomes multistage and starts from the innermost particles relatively well reproduced with S-W model, whereas the reversal of the stripes, starts from the outermost particles and has no analog in S-W model. Practical consequences of the findings are discussed.