arXiv subjects

Deborah Schlagel

Publications and source records attributed to Deborah Schlagel.

3 recordsLinked to original sources

arXiv2024

Coexistence of Ferromagnetism and Antiferromagnetic Dimers in Topological Insulators

The addition of magnetic impurities in topological insulators can drive ferromagnetic order that leads to novel quantum anomalous Hall transport well below the Curie temperature. The fragility of the quantized regime has been ascribed to the random nature of the magnetic moment distribution. Here, we refine this hypothesis by using inelastic neutron scattering and density-functional theory calculations to show that two antagonistic components define the magnetism in Mn-substituted SnTe, thereby limiting the effectiveness of dilute magnetic TIs. One component is strongly bound antiferromagnetic dimers that compete with ferromagnetic order. The other component consists of undimerized moments where ferromagnetic order develops via long-range interactions.

cond-mat.str-el↗

arXiv2023

Quasiparticle spectroscopy in technologically-relevant niobium using London penetration depth measurements

London penetration depth was measured in niobium foils, thin films, single crystals, and superconducting radio-frequency (SRF) cavity pieces cut out from different places. The low-temperature (T<Tc/3) variation, sensitive to the low-energy quasiparticles with states inside the superconducting gap, differs dramatically between different types of samples. With the help of phenomenological modeling, we correlate these different behaviors with known pair-breaking mechanisms and show that such measurements may help distinguish between different pair-breaking mechanisms, such as niobium hydrides and two-level systems (TLS). The conclusions also apply to SRF cavities when tracking the temperature-dependent quality factor and the resonant frequency.

cond-mat.supr-con↗

arXiv2021

Evidence for Temperature Chaos in Spin Glasses

We study the field cooled magnetization of a CuMn spin glass under temperature perturbations. The $T$-cycling curves are compared with the reference curve without temperature cycling. There is a crossover from the cumulative aging region to noncumulative aging region as the temperature change is increased. The cumulative aging range scales with the chaos length $\ell_\mathrm{c}$, becoming comparable to the correlation length, $ξ$, at the crossover boundary. The extracted chaos exponent, $ζ= 1.1$, is in agreement with theoretical predictions. Our results strongly suggest temperature chaos exists in real spin glasses system.

cond-mat.dis-nn↗