Juan Trastoy

Growth-Induced In-Plane Uniaxial Anisotropy in V 2 O 3 /Ni Films

We report on a strain-induced and temperature dependent uniaxial anisotropy in V2O3/Ni hybrid thin films, manifested through the interfacial strain and sample microstructure, and its consequences on the angular dependent magnetization reversal. X-ray diffraction and reciprocal space maps identify the in-plane crystalline axes of the V2O3; atomic force and scanning electron microscopy reveal oriented rips in the film microstructure. Quasi-static magnetometry and dynamic ferromagnetic resonance measurements identify a uniaxial magnetic easy axis along the rips. Comparison with films grown on sapphire without rips shows a combined contribution from strain and microstructure in the V2O3/Ni films. Magnetization reversal characteristics captured by angular-dependent first order reversal curve measurements indicate a strong domain wall pinning along the direction orthogonal to the rips, inducing an angular-dependent change in the reversal mechanism. The resultant anisotropy is tunable with temperature and is most pronounced at room temperature, which is beneficial for potential device applications.

Enhanced metal–insulator transition in V 2 O 3 by thermal quenching after growth

The properties of oxides are critically controlled by the oxygen stoichiometry. Minimal variations in oxygen content can lead to vast changes in their properties. The addition of oxygen during synthesis may not be a precise enough knob for tuning the oxygen stoichiometry when the material has several stable and close oxidation states. We use sputtered V2O3 films as an example to show that rapid transfer of the sample away from the heating element after growth causes a temperature decrease (quenching) quick enough to freeze the correct oxygen stoichiometry in the sample. This procedure has allowed us to improve dramatically the V2O3 electronic properties without any adverse measurable effects on the structural properties. In this fashion, the metal–insulator transition resistance change was increased by two orders of magnitude, while the transition width was decreased by 20xa0K.

Criticality in the Brain: Evidence and Implications for Neuromorphic Computing

We have discovered an unexpected correlation between the operational temperature of the brain and cognitive abilities across a wide variety of animal species. This correlation is extracted from available data in the literature of the temperature range Δ T at which an animals brain can operate and its encephalization quotient EQ, which can be used as a proxy for cognitive ability. In particular, we found a power-law dependence between Δ T and EQ. These data support the theory that the brain behaves as a critical system where temperature is one of the critical parameters, tuning the performance of the neural network.