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Abstract Chromia (Cr₂O₃) is a magnetoelectric oxide that permits voltage‐control of the antiferromagnetic (AFM) order, but it suffers technological constraints due to its low Néel Temperature (T_N≈307 K) and the need of a symmetry‐breaking applied magnetic field to achieve reversal of the Néel vector. Recently, boron (B) doping of Cr₂O₃films led to an increaseT_N>400 K and allowed the realization of voltage magnetic‐field free controlled Néel vector rotation. Here, the impact of B doping is directly imaged on the formation of AFM domains in Cr₂O₃thin films and elucidates the mechanism of voltage‐controlled manipulation of the spin structure using nitrogen‐vacancy (NV) scanning probe magnetometry. A stark reduction and thickness dependence of domain size in B‐doped Cr₂O₃(B:Cr₂O₃) films is found, explained by the increased germ density, likely associated with the B doping. By reconstructing the surface magnetization from the NV stray‐field maps, a qualitative distinction between the undoped and B‐doped Cr₂O₃films is found, manifested by the histogram distribution of the AFM ordering, that is, 180°domains for pure films, and 90°domains for B:Cr₂O₃films. Additionally, NV imaging of voltage‐controlled B‐doped Cr₂O₃devices corroborates the 90°rotation of the AFM domains observed in magnetotransport measurement. 

Abstract Boron (B) alloying transforms the magnetoelectric antiferromagnet Cr₂O₃into 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:Cr₂O₃films. 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 Al₂O₃substrates. 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. HereT_Nenhances from 334 K prior to annealing, to 477 K after annealing for several hours. Scaling analysis determinesT_Nas 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.