arXiv subjects

M. L. McLanahan

Publications and source records attributed to M. L. McLanahan.

3 recordsLinked to original sources

arXiv2026

How Electrons Become Mobile in a Colossal Dielectric -- Fe$_2$TiO$_5$

We measure the colossal permittivity in single crystal Fe$_2$TiO$_5$ using broadband spectroscopy in the frequency range 20 Hz - 1 MHz. The relaxation response is analyzed using a Debye-like model with Arrhenius activation in two different ways and yields an energy barrier of 286.1 $\pm$ 2.8 meV. DC transport yields an activation energy of 288.8 $\pm$ 2.8 meV. These results strongly imply that the energy barrier for localized dipole motion and itinerant charge transport originate from the same atom-level forces. A further implication is that colossal dielectric behavior is a microscopic bulk phenomenon arising from a system on brink of metallicity.

cond-mat.mtrl-sci↗

arXiv2026

Suppression of Thermal Conductivity via Singlet-Dominated Scattering in TmFeO$_3$

We measured the thermal conductivity of the rare-earth orthoferrites, $R$FeO$_3$, where $R$ = Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb from 3 K to 300 K and see an anomalous strong suppression for TmFeO$_3$ over most of the temperature range. Using a Debye thermal transport model, we demonstrate that this suppression is due to resonant scattering between phonons and the Tm$^{3+}$ $4f$ singlet crystal field levels. The implications of these results are discussed in context of thermal conductivity studies in quantum magnets.

cond-mat.mtrl-sci↗

arXiv2025

Quantum Spin Relaxation with THz Attempt Frequency in the 1/3-Fire, 2/3-Ice Ferrimagnet SmMn$_2$Ge$_2$

Ferrimagnets in which half the spins are disordered and half ordered, so-called half-fire, half-ice state, have been advanced theoretically as a route towards realizing exotic magnetic ground states. Here we demonstrate novel single-spin resonance in SmMn$_2$Ge$_2$, a 1/3-fire, 2/3-ice material. Using ac-susceptibility in the frequency range 0.1 Hz - 1 kHz we find a Debye-like resonance with Orbach relaxation temperature dependence, yielding an energy barrier $E_B \approx 840$ $k_B$ and attempt frequencies in the THz range. These quantities strongly suggest single-spin relaxation among paramagnetic Sm spins where the flipping field is provided by the FM-ordered Mn spins at domain boundaries, a direct outcome of the 1/3-fire, 2/3-ice state.

cond-mat.mtrl-sci↗