Engineering topics

Garcia, Flavio

Publications and source records attributed to Garcia, Flavio.

2 records

DOE OSTI2022

Memristive Effects in Nanopatterned Permalloy Kagomé Array

Here, we study memristive effects in kagomé nanopatterned permalloy. We observe that at low frequencies a thermistor effect is present, a phenomenon arising due to the lithography and absent in similar experiments for thin films. However, we also show via an independent anisotropic magnetoresistive study that a small hysteresis accounting for 1% of the effect is not attributable to a thermistive effect. Such an effect is also confirmed by a careful subtraction scheme between nearby thermal hysteresis. In the millihertz regime, an effective model is provided to describe the experimental results for the thermistor, showing that there should be a crossover from the millihertz to the gigahertz, from a thermistor to a memristive effect for nanopatterned permalloy.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Pressure-tuning of the electronic and magnetic properties of EuPt 2 Si 2

Using the element and orbital selectivity of x-ray absorption spectroscopy at Eu and Pt L 3 edges we investigate the effects of the lattice contraction, induced by temperature and external pressure, on the magnetic and electronic properties of the EuPt 2 Si 2 system. Our findings point to a clear relationship between the volume and the Eu valence in this material. From XANES experiments as a function of pressure we show that the Europium valence tends to stabilize at 3+ for pressures up to 27 GPa. The XMCD results demonstrate that pressure induced valence change of the Europium ion leads to a suppression of the magnetic ordering of the material. Finally, altogether our results provide direct evidence that Eu-4f /5d electronic hybridization effects underlie the mechanism that regulates the valence and magnetic ordering in this material.

36 MATERIALS SCIENCE↗