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

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