arXiv subjects

Erik Walendy

Publications and source records attributed to Erik Walendy.

3 recordsLinked to original sources

arXiv2026

Critical behavior and evidence of dimensional crossover in quasi-two-dimensional Li$_2$FeSiO$_4$

We report thermal expansion and heat capacity studies on Li$_2$FeSiO$_4$ single crystals which enable us to investigate the critical behavior in the magnetically quasi-two-dimensional (2D) material. Pronounced $\lambda$-shaped anomalies at the magnetic ordering temperature $T_{\rm N}$ imply significant magneto-elastic coupling. Our analysis of both the thermal expansion and the specific heat data implies the crossover from 2D Ising-like behavior for $|(T-T_{\rm N})/T_{\rm N}|>0.3$ to 3D Ising behavior \rev{below $\simeq 1.3\times T_{\rm N}$. The 2D-like behavior is further supported by density functional calculations which show minimal dispersion perpendicular to the crystallographic $ac$ planes of the layered structure, thereby indicating the 2D nature of magnetism at higher temperatures.} Our results extend the available model materials of quasi-2D magnetism to a high-spin $S=2$ system with tetrahedrally coordinated Fe$^{2+}$-ions, thereby illustrating how magnetic order evolves in a 2D Ising-like system with orbital degrees of freedom.

cond-mat.str-el↗

arXiv2025

Elucidating the origin of long-range ferromagnetic order in Fe$_3$GeTe$_2$ by low-energy magnon excitation studies

We report a detailed high-field/high-frequency ferromagnetic resonance (HF-FMR) study of low-energy magnon excitations in the van der Waals ferromagnet Fe$_3$GeTe$_2$. At 2 K, the field dependence of the magnon branches is well described by a semiclassical domain-based model, from which we extract key microscopic parameters including the anisotropy gap $Δ= 170\pm 4$ GHz, the anisotropy field $B_{\rm A} = 5.85\pm 0.08$ T, and the effective $g$-factor $g_{\rm ab}\simeq g_{\rm c} = 2.07(4)$. Furthermore the uniaxial anisotropy constant was determined to be $K = (10.5\pm 0.23) \times 10^{-6}$ erg/cm$^3$. Anisotropic short-range magnetic order persists above $T_{\rm C}$ up to approximately 270 K, as evidenced by a finite anisotropy gap and anisotropic shifts in the FMR resonance fields. Both results clearly show the presence of anisotropic local magnetic fields well above $T_{\rm C}$. Our findings underscore the crucial role of magneto-crystalline anisotropy in driving long-range magnetic order in Fe$_3$GeTe$_2$.

cond-mat.str-el↗

arXiv2025

Anisotropic magnetic phase diagrams, tricriticality, and spin-reorientation in high-pressure grown SmCrO$_3$ single crystals

SmCrO$_3$ single crystals were successfully grown utilizing the high-pressure optical floating-zone method and their crystal structure, magnetization behavior, and magnetic phase diagrams were thoroughly investigated. Magnetic studies were conducted for fields applied along all principal crystallographic directions, with measurements taken at temperatures as low as 0.4 K and magnetic fields up to 14 T. The single crystal growth parameters are reported and the orthorhombic structure with the centrosymmetric space group $Pbnm$ is confirmed. Long-range order of the Cr$^{3+}$ and Sm$^{3+}$ magnetic sublattices evolves at $T_{\rm N}$ = 192 K and $T_{\rm N2}$=3 K, respectively. In contrast to previous studies on polycrystals our single crystal data imply a discontinuous and one-step spin-reorientation (SR) of net magnetic moments $\tilde{M}$ from the $c$ axis into the $ab$ plane at zero magnetic field at $T_{\rm SR}$=33 K. Its discontinuous nature is maintained if $B$ is applied $||c$ axis but tricritical behavior and a triple point is found for $B||a$ axis. While our data are consistent with the magnetic representation $Γ_4$ for $T > T_{\mathrm {SR}}$, the size and in-plane direction of the observed net magnetic moment disagree to previously proposed spin configurations, i.e., $Γ_1$ and $Γ_2$, for the spin-reoriented phases. In general, our high-quality single crystals enable us to revisit the phase diagram and to clarify the complex magnetism in SmCrO3 arising from the interplay of anisotropic 3$d$ and 4$f$ magnetic sublattices.

cond-mat.str-el↗