Wasp -- Waisted loop and Spin frustration in Dy$_{2-x}$Eu$_x$Ti$_2$O$_7$ Pyrochlore
arXiv:1907.11383
The paper investigates how substituting Eu for Dy in the pyrochlore Dy₂₋ₓEuₓTi₂O₇ affects its lattice vibrations and magnetic behavior, revealing dipolar exchange interactions, wasp‑waisted hysteresis loops, and distinct spin‑freezing transitions for Dy³⁺ and Eu³⁺ ions.
Abstract
The Raman spectroscopy and AC and DC magnetization of Dy$_{2-x}$Eu$_x$Ti$_2$O$_7$ have been investigated. In Raman Spectroscopy, the systematic shift in all phonon modes with Eu content in Dy$_{2-x}$Eu$_x$Ti$_2$O$_7$ confirms that Dy$^{3+}$ ion is substituted by Eu3+ ions. High concentration of Eu induces the dipolar exchange interactions and crystal-field interactions in Dy$_{2-x}$Eu$_x$Ti$_2$O$_7$. Rich Eu content samples (x=1.8 and 1.9) show the existence of wasp-waisted hysteresis loop and that can be attributed to the coexistence of dipolar field and anisotropy exchange interaction. AC susceptibility shows two single ion spin freezing transitions corresponding to Dy$^{3+}$ and Eu$^{3+}$ ions respectively in x = 1.5, 1.8, 1.9 samples.
25 pages, 7 figures