arXiv subjects

Jacob Freyermuth

Publications and source records attributed to Jacob Freyermuth.

3 recordsLinked to original sources

arXiv2026

Domain-wall drift in a ferrimagnet induced by a linearly oscillating in-plane magnetic field

We investigate ferrimagnetic domain-wall dynamics under linearly oscillating in-plane magnetic fields. Starting from a ferrimagnetic Lagrangian that retains the field-dependent contribution to the kinetic energy, we derive collective-coordinate equations for the domain-wall position and azimuthal angle. This formulation makes explicit the field-induced inertial terms, including Coriolis-, Euler-, and centrifugal-like contributions, and clarifies how they couple translational and azimuthal dynamics. For an oscillating in-plane field supplemented by a weak static out-of-plane bias field, we show that periodic switching of the wall angle can be rectified into a finite average domain-wall velocity. At low drive frequencies, where the wall angle follows the oscillating field, the induced drift is proportional to the drive frequency rather than the field amplitude, while above a cutoff frequency the wall angle can no longer follow the drive and the average motion is suppressed. Micromagnetic simulations confirm the analytical predictions and demonstrate that the magnitude and direction of the drift can be tuned by the net spin density. These results identify linearly oscillating fields as a mechanism for frequency-controlled domain-wall motion in ferrimagnets and highlight the role of inertial spin dynamics near magnetic compensation.

cond-mat.str-el↗

arXiv2019

Doping-dependent phonon anomaly and charge-order phenomena in the HgBa$_{2}$CuO$_{4+\delta}$ and HgBa$_{2}$CaCu$_{2}$O$_{6+\delta}$

Using resonant X-ray diffraction and Raman spectroscopy, we study charge correlations and lattice dynamics in two model cuprates, HgBa$_{2}$CuO$_{4+\delta}$ and HgBa$_{2}$CaCu$_{2}$O$_{6+\delta}$. We observe a maximum of the characteristic charge order temperature around the same hole concentration ($p \approx 0.09$) in both compounds, and concomitant pronounced anomalies in the lattice dynamics that involve the motion of atoms in and/or adjacent to the CuO$_2$ layers. These anomalies are already present at room temperature, and therefore precede the formation of the static charge correlations, and we attribute them to an instability of the CuO$_2$ layers. Our finding implies that the charge order in the cuprates is an emergent phenomenon, driven by a fundamental variation in both lattice and electronic properties as a function of doping.

cond-mat.supr-con↗

arXiv2018

Growth and characterization of HgBa2CaCu2O6+d and HgBa2Ca2Cu3O8+d crystals

We report the successful synthesis of single-crystalline cuprate superconductors HgBa$_{2}$CaCu$_{2}$O$_{6+\delta}$ and HgBa$_{2}$Ca$_{2}$Cu$_{3}$O$_{8+\delta}$. These compounds are well-known for their high optimal superconducting critical temperatures of $T_\mathrm{c}$ = 128 K and 134 K at ambient pressure, respectively, and for their challenging synthesis. Using a conventional quartz-tube encapsulation method and a two-layer encapsulation method that utilizes custom-built high-pressure furnaces, we are able to grow single crystals with linear dimensions up to several millimeters parallel to the CuO$_2$ planes. Extended post-growth anneals are shown to lead to sharp superconducting transitions, indicative of high macroscopic homogeneity. X-ray diffraction and polarized Raman spectroscopy are identified as viable methods to resolve the seemingly unavoidable inter-growth of the two compounds. Our work helps to remove obstacles toward the study of these model cuprate systems with experimental probes that require sizable high-quality crystals.

cond-mat.supr-con↗