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Gradual switching between multiple resistance levels is desirable for analog in-memory computing using resistive random-access memory (RRAM). However, the filamentary switching of HfOx-based conventional RRAM often yields only two stable memory states instead of gradual switching between multiple resistance states. Here, we demonstrate that a thermal barrier of Ge2Sb2Te5 (GST) between HfOx and the bottom electrode (TiN) enables wider and weaker filaments, by promoting heat spreading laterally inside the HfOx. Scanning thermal microscopy suggests that HfOx + GST devices have a wider heating region than control devices with only HfOx, indicating the formation of a wider filament. Such wider filaments can have multiple stable conduction paths, resulting in a memory device with more gradual and linear switching. The thermally enhanced HfOx + GST devices also have higher on/off ratio (>103) than control devices (<102) and a median set voltage lower by approximately 1 V (∼35%), with a corresponding reduction of the switching power. Our HfOx + GST RRAM shows 2× gradual switching range using fast (∼ns) identical pulse trains with amplitude less than 2 V. [ABSTRACT FROM AUTHOR]

Magnetization switching induced by spin–orbit torque is of fundamental interest for developing spintronic devices with low-power consumption and nonvolatility. Here, we report on the spin–orbit torque induced magnetization switching behavior of (001) oriented tetragonal Heusler alloy D022-Mn3Ga films with an intrinsic ferrimagnetic spin structure grown on the GaAs(001) substrate by molecular-beam epitaxy. The out-of-plane hysteresis loop and anomalous Hall effect demonstrated a large perpendicular magnetic anisotropy and low saturation magnetization of D022-Mn3Ga thin films. The spin–orbit torque induced magnetization switching has been realized in D022-Mn3Ga/Pt heterostructure based Hall devices under an in-plane external field. It is found that the critical switching current density Jc is much smaller than that of the L10-MnGa/heavy metal system. Besides, both a dampinglike effective field HDL and a fieldlike effective field HFL are quantified by performing harmonic Hall voltage measurements. All these results indicate that ferrimagnetic D022-Mn3Ga can be a promising candidate material for realizing high-density and energy-efficient spintronic devices. [ABSTRACT FROM AUTHOR]