Wasp -- Waisted loop and Spin frustration in Dy$_{2-x}$Eu$_x$Ti$_2$O$_7$ Pyrochlore

TL;DR

This study investigates how Eu substitution affects the magnetic and vibrational properties of Dy$_{2-x}$Eu$_x$Ti$_2$O$_7$ pyrochlore, revealing complex magnetic interactions and spin freezing phenomena.

Contribution

It provides new insights into the effects of Eu doping on phonon modes, magnetic interactions, and spin dynamics in Dy-based pyrochlore materials.

Findings

Eu substitution shifts phonon modes systematically.

High Eu content induces wasp-waisted hysteresis loops.

Two distinct spin freezing transitions observed.

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.