Emergence of Spin Ice freezing in Dy$_2$Ti$_{1.8}$Mn$_{0.2}$O$_7$

Abstract

We herein present the spin freezing dynamics of stuffed polycrystalline compound Dy$_2$Ti$_{1.8}$Mn$_{0.2}$O$_7$. In Dy$_2$Ti$_2$O$_7$, spin freezes with ice-like spin relaxations at a temperature around 3 K (T$_i$) along with another spin freezing at a temperature around 0.7 K (T\textless T$_i$). These relaxations can be observed prominently with an application of varying DC magnetic field bias and applied AC-field. We show here that with fractional inclusion of Mn at the Ti site in Dy$_2$Ti$_2$O$_7$, there is a significant shift in these temperatures. In Dy$_2$Ti$_{1.8}$Mn$_{0.2}$O$_7$ the T$_i$ shifts to a higher temperature around 5 K and freezing belonging to T\textless T$_i$ shifts to 2.5 K without any application of external DC Bias and/or AC-field. The inclusion of Mn at Ti site also enhances the ferromagnetic interaction for Dy$_2$Ti$_{1.8}$Mn$_{0.2}$O$_7$ as compared to Dy$_2$Ti$_2$O$_7$. Arrhenius fit of freezing temperature with frequency for Dy$_2$Ti$_{1.8}$Mn$_{0.2}$O$_7$ shows that these spin relaxations at T$_i$ and T\textless T$_i$ are thermally induced. Low-temperature structural change in lattice parameters and crystal field phonon coupling has been studied using synchrotron x-ray diffraction. Debye-Gruineisen analysis of temperature-dependent lattice volume shows the emergence of crystal field phonon coupling at a much higher temperature (70 K) in Dy$_2$Ti$_{1.8}$Mn$_{0.2}$O$_7$ in contrast to 40 K in Dy$_2$Ti$_2$O$_7$. These findings make Dy$_2$Ti$_{1.8}$Mn$_{0.2}$O$_7$ a suitable system to explore the application of the spin ice phenomenon at a workable temperature.