Ather Mahmood

This perspective article explores the potential of two-dimensional electron and hole gases at oxide/oxide interfaces as promising conduction channels in energy-efficient spintronic devices for memory and logic applications. Magneto-electric and ferro-electric device architectures are considered, highlighting their advantages in integrating non-volatility with ultra-fast switching capabilities. We emphasize the significance of spin–orbit coupling in generating robust spin currents and examine how the Rashba and inverse Edelstein effects can be harnessed in device operations. Specific heterostructures, including HfO₂/SrTiO₃, Cr₂O₃/TiO_2-x, and ZrO_2-x-based systems, are reviewed in terms of their material properties, interface stability, and suitability for practical implementation.

We study the effect of strain on the magnetic properties and magnetization configurations in nanogranular Fe _x Ge 1 − x films ( x = 0.53 ± 0.05 ) with and without B20 FeGe nanocrystals surrounded by an amorphous structure. Relaxed films on amorphous silicon nitride membranes reveal a disordered skyrmion phase while films near and on top of a rigid substrate favor ferromagnetism and an anisotropic hybridization of Fe d levels and spin-polarized Ge sp band states. The weakly coupled topological states emerge at room temperature and become more abundant at cryogenic temperatures without showing indications of pinning at defects or confinement to individual grains. These results demonstrate the possibility to control magnetic exchange and topological magnetism by strain and inform magnetoelasticity-mediated voltage control of topological phases in amorphous quantum materials.

Boron (B) alloying transforms the magnetoelectric antiferromagnet Cr₂O₃ into a multifunctional single‐phase material which enables electric field driven π/2 rotation of the Néel vector. Nonvolatile, voltage‐controlled Néel vector rotation is a much‐desired material property in the context of antiferromagnetic spintronics enabling ultralow power, ultrafast, nonvolatile memory, and logic device applications. Néel vector rotation is detected with the help of heavy metal (Pt) Hall‐bars in proximity of pulsed laser deposited B:Cr₂O₃ films. To facilitate operation of B:Cr₂O₃‐based devices in CMOS (complementary metal‐oxide semiconductor) environments, the Néel temperature, T_N, of the functional film must be tunable to values significantly above room temperature. Cold neutron depth profiling and X‐ray photoemission spectroscopy depth profiling reveal thermally activated B‐accumulation at the B:Cr₂O₃/ vacuum interface in thin films deposited on Al₂O₃ substrates. The B‐enrichment is attributed to surface segregation. Magnetotransport data confirm B‐accumulation at the interface within a layer of ≈50 nm thick where the device properties reside. Here T_N enhances from 334 K prior to annealing, to 477 K after annealing for several hours. Scaling analysis determines T_N as a function of the annealing temperature. Stability of post‐annealing device properties is evident from reproducible Néel vector rotation at 370 K performed over the course of weeks.

We study the influence of defects in Co/Pt multilayers on the room-temperature magnetization reversal and relaxation mechanisms via angle-dependent magnetic viscosity and coercive field measurements. The data reveal a transition from pinning-dominated domain wall propagation to a sequence of pinning-dominated and uniform switching, with increasing tilt away from the normal direction. The leading role of the dendritic domain wall propagation in the nanogranular exchange-coupled films is corroborated by the scaling of relaxation times, the angular dependence of the coercive field, and Kerr microscopy.

Multi-functional thin films of boron (B) doped Cr₂O₃ exhibit voltage-controlled and nonvolatile Néel vector reorientation in the absence of an applied magnetic field, H. Toggling of antiferromagnetic states is demonstrated in prototype device structures at CMOS compatible temperatures between 300 and 400 K. The boundary magnetization associated with the Néel vector orientation serves as state variable which is read via magnetoresistive detection in a Pt Hall bar adjacent to the B:Cr₂O₃ film. Switching of the Hall voltage between zero and non-zero values implies Néel vector rotation by 90 degrees. Combined magnetometry, spin resolved inverse photoemission, electric transport and scanning probe microscopy measurements reveal B-dependent T_N and resistivity enhancement, spin-canting, anisotropy reduction, dynamic polarization hysteresis and gate voltage dependent orientation of boundary magnetization. The combined effect enables H = 0, voltage controlled, nonvolatile Néel vector rotation at high-temperature. Theoretical modeling estimates switching speeds of about 100 ps making B:Cr₂O₃ a promising multifunctional single-phase material for energy efficient nonvolatile CMOS compatible memory applications.