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Creators/Authors contains: "Tsymbal, Evgeny Y."

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  1. Abstract

    Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics, where an AFM Néel vector is used as a state variable. Efficient electric control and detection of the Néel vector are critical for spintronic applications. This review article features fundamental properties of AFM tunnel junctions (AFMTJs) as spintronic devices where such electric control and detection can be realized. We emphasize critical requirements for observing a large tunneling magnetoresistance (TMR) effect in AFMTJs with collinear and noncollinear AFM electrodes, such as a momentum-dependent spin polarization and Néel spin currents. We further discuss spin torques in AFMTJs that are capable of Néel vector switching. Overall, AFMTJs have potential to become a new standard for spintronics providing larger magnetoresistive effects, few orders of magnitude faster switching speed, and much higher packing density than conventional magnetic tunnel junctions (MTJs).

     
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    Free, publicly-accessible full text available December 1, 2025
  2. The wider application of spintronic devices requires the development of new material platforms that can efficiently manipulate spin. Bismuthate-based superconductors are centrosymmetric systems that are generally thought to offer weak spin–orbit coupling. Here, we report a large spin–orbit torque driven by spin polarization generated in heterostructures based on the bismuthate BaPb1-xBixO3 (which is in a non-superconducting state). Using spin-torque ferromagnetic resonance and d.c. non-linear Hall measurements, we measure a spin–orbit torque efficiency of around 2.7 and demonstrate current driven magnetization switching at current densities of 4×10^5 A〖cm〗^(-2). We suggest that the unexpectedly large current-induced torques could be the result of an orbital Rashba effect associated with local inversion symmetry breaking in BaPb1-xBixO3. 
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  3. The recent observation of ferroelectricity in the metastable phases of binary metal oxides, such as HfO2, ZrO2, Hf0.5Zr0.5O2, and Ga2O3, has garnered a lot of attention. These metastable ferroelectric phases are typically stabilized using epitaxial strain, alloying, or defect engineering. Here, we propose that hole doping plays a key role in the stabilization of polar phases in binary metal oxides. Using first-principles density-functional-theory calculations, we show that holes in these oxides mainly occupy one of the two oxygen sublattices. This hole localization, which is more pronounced in the polar phase than in the nonpolar phase, lowers the electrostatic energy of the system, and makes the polar phase more stable at sufficiently large concentrations. We demonstrate that this electrostatic mechanism is responsible for stabilization of the ferroelectric phase of HfO2 aliovalently doped with elements that introduce holes to the system, such as La and N. Finally, we show that spontaneous polarization in HfO2 is robust to hole doping, and a large polarization persists even under a high concentration of holes. 
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