The electric manipulation of antiferromagnets has become an area of great interest recently for zero-stray-field spintronic devices, and for their rich spin dynamics. Generally, the application of antiferromagnetic media for information memories and storage requires a heterostructure with a ferromagnetic layer for readout through the exchange-bias field. In magnetoelectric and multiferroic antiferromagnets, the exchange coupling exerts an additional impediment (energy barrier) to magnetization reversal by the applied magnetoelectric energy. We proposed and verified a method to overcome this barrier. We controlled the energy required for switching the magnetic domains in magnetoelectric Cr 2 O 3 films by compensating the exchange-coupling energy from the ferromagnetic layer with the Zeeman energy of a small volumetric spontaneous magnetization found for the sputtered Cr 2 O 3 films. Based on a simplified phenomenological model of the field-cooling process, the magnetic and electric fields required for switching could be tuned. As an example, the switching of antiferromagnetic domains around a zero-threshold electric field was demonstrated at a magnetic field of 2.6 kOe.
We investigated perpendicular exchange bias switching by a magnetoelectric field cooling process in a Pt-spacer-inserted Cr2O3/Co exchange-coupled system exhibiting small Cr2O3 magnetization. Although higher magnetoelectric switching energies with decreasing Cr2O3 thickness due to the exchange bias were reported in Cr2O3/Co all-thin-film systems, in this study, we demonstrated low-energy switching in a magnetoelectric field cool process regardless of the exchange-bias magnitude; we balanced the exchange-bias energy with the Zeeman energy associated with finite magnetization in Cr2O3. We proposed a guideline for realizing low-energy switching in thin Cr2O3 samples.
Antiferromagnets and ferrimagnets with a low net magnetic moment are key components for future spintronic devices because they enable high-integration and high-speed (on the order of THz) operations. Cr 2 O 3 is one of the few antiferromagnets that can achieve 180 manipulation of its spin by electrical means. In this study, the authors developed a new functional material, Cr 2 O 3 , with tunable parasitic magnetization. The authors demonstrate both magnitude and direction tunability of parasitic magnetization in Cr 2 O 3 thin films by doping. A sublattice magnetization reduction and displacement-induced nonequivalent Cr moments by site-selective substitution of nonmagnetic elements are inferred to be the origin of the parasitic magnetization. By utilizing the tunable parasitic magnetization, the authors demonstrate the manipulation of antiferromagnetic single domain. In addition, the authors confirm the low-electric-field switching ability of the antiferromagnetic spin in a doped Cr 2 O 3 /Co exchange coupling system. Such tunable parasitic magnetization enables easy manipulation and detection of antiferromagnetic spin and provides a platform for further understanding of antiferromagnets and research opportunities in innovative spintronics device applications.For a decade, ferromagnetic materials have played a prominent role in the development of spintronics. Ferromagnet (FM)based spintronics have resulted in unique high-performance devices, such as magnetoresistive random-access memory (MRAM). [1] However, specific problems, such as magnetic interferences, are a considerable barrier to further integration of these devices, restricting their future development. One way to overcome such problems is to utilize antiferromagnets (AFMs) or ferrimagnets with low net magnetic moments instead of FMs. As stated by N eel, [2] the high potential of AFMs has been recognized for a long time; AFMs do not generate stray fields, are stable in the presence of an external magnetic field, and have THz precession frequency, which enable the realization of high-integration and ultra-high-speed operation devices. Although the difficulty in conventional manipulation and detection of antiferromagnetic spin restricts its spintronics applications, these processes have increasingly become more feasible due to recent progress. [3][4][5] In particular, 90 control (uniaxial anisotropy control) of antiferromagnetic spin become more feasible. 90 manipulations of the antiferromagnetic spin using an electric current were demonstrated for FeRh through current-induced Joule heating, [6,7] and CuMnAs through spin-orbit torque. [8,9] The corresponding detection techniques, such as anisotropic magnetoresistance (AMR), [8,10,11] tunnel anisotropic magnetoresistance (TAMR), [12] and spin Hall magnetoresistance (SMR) of AFM, [13] which can detect 90 difference in antiferromagnetic spin has also been developed. In contrast, 180 control (unidirectional anisotropy control) of antiferromagnetic spins has been rarely demonstrated, while it enable higher perfo...
Chromium(III) oxide is a classical collinear antiferromagnet with a linear magnetoelectric effect. We are presenting the measurements of the magnetoelectric susceptibility α of a sputter-deposited 500-nm film and a bulk single-crystal of Cr2O3. We investigated the magnetic phase-transition and the critical exponent β of the sublattice magnetization near Néel temperature. For the films, an exponent of 0.49(1) was found below 293 K, and changed to 1.06(4) near the Néel temperature of 298 K. For the single-crystal, the exponent was constant at 0.324(4). We investigated the reversal probability of antiferromagnetic domains during magnetoelectric field cooling. For the sputtered films, reversal probability was zero above 298 K and stabilized only below 293 K. We attribute this behavior to formation of grains during film growth, which gives different intergrain and intragrain exchange-coupling energies. For the single-crystal, reversal probability was stabilized immediately at the Néel temperature of 307.6 K.
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