Structural and magnetic properties of a new cubic spinel LiRhMnO4

We report the structural and magnetic properties of a new system LiRhMnO$₄$ (LRMO) through x-ray diffraction, bulk magnetization, heat capacity and $⁷$Li nuclear magnetic resonance (NMR) measurements. LRMO crystallizes in the cubic space group $\mathit{Fd}$$\bar{3}$$\mathit{m}$. From the DC susceptibility data, we obtained the Curie-Weiss temperature $\mathrmθ_{\mathrm{CW}}$ = -26 K and Curie constant $\mathit{C}$ = 1.79 Kcm$³$/mol suggesting antiferromagnetic correlations among the magnetic Mn$⁴⁺$ ions with an effective spin $\mathit{S}$ = $\frac{3}{2}$. At $\mathit{H}$ = 50 Oe, the field cooled and zero-field cooled magnetizations bifurcate at a freezing temperature, $T_f$ = 4.45 K, which yields the frustration parameter $\mathit{f=\frac{\midθ_CW\mid}{T_f}}>$5. AC susceptibility, shows a cusp-like peak at around $T_f$, with the peak position shifting as a function of the driving frequency, confirming a spin-glass-like transition in LRMO. LRMO also shows typical spin-glass characteristics such as memory effect, aging effect and relaxation. In the heat capacity, there is no sharp anomaly down to 2 K indicative of long-range ordering. The field sweep $⁷$Li NMR spectra show broadening with decreasing temperature without any spectral line shift. The $⁷$Li NMR spin-lattice and spin-spin relaxation rates also show anomalies due to spin freezing near $T_f$.