arXiv subjects

Ashiwini Balodhi

Publications and source records attributed to Ashiwini Balodhi.

7 recordsLinked to original sources

arXiv2024

Synthesis, structural and magnetic characterizations of Li$_4$Cu$_{1-x}$Ni$_x$TeO$_6$ ( $x$ = 0, 0.1, 0.2, 0.5, and 1)

We investigated the effect of Ni doping in a recently proposed quantum spin liquid (QSL) candidate Li$_4$CuTeO$_6$. We performed a comprehensive study on the structural and magnetic properties. We find that the anti-site disorder between Li$^+$ and Cu$^{2+}$ persists until 50\% Ni doping in which Ni and Cu occupy different crystallographic sites. As a result, while Cu sits in both triangular and honeycomb layers in Li$_4$CuTeO$_6$, Ni forms only honeycomb layer in Li$_4$NiTeO$_6$ and Li$_4$Cu$_{0.5}$Ni$_{0.5}$TeO$_6$. Our magnetic susceptibility measurements show that the Weiss temperature decreases from -145.68 K in Li$_4$CuTeO$_6$ to -6.15 K in Li$_4$NiTeO$_6$ as Ni doping increases, and find no hint of magnetic ordering or freezing down to 1.8 K. Our analysis implies the existence of abundant low energy excitations in these materials.

cond-mat.mtrl-sci↗

arXiv2018

Effect of disorder on the quantum spin liquid candidate Na$_4$Ir$_3$O$_8$

We report on the effects of introducing magnetic and non-magnetic disorder in the hyperkagome iridate quantum spin liquid (QSL) candidate Na$_4$Ir$_3$O$_8$ by partially replacing Ir$^{4+}$ ($S = 1/2$) with Ru$^{4+}$ ($S = 1$) or Ti$^{4+}$ ($S = 0$). Specifically, we synthesized Na$_4$(Ir$_{1-x}$Ru$_x$)$_3$O$_8 (x = 0.05, 0.10, 0.2, 0.3)$ and Na$_4$Ir$_{2.7}$Ti$_{0.3}$O$_8$ samples and measured electrical transport, AC and DC magnetization, and heat capacity down to $T = 1.8$ K. Na$_4$Ir$_3$O$_8$ is associated with a large Weiss temperature $θ= -650$ K, a broad anomaly in magnetic heat capacity C$_{mag}$ at T $\approx25$ K, low temperature power-law heat capacity, and spin glass freezing below $T_f \approx 6$ K. We track the change in these characteristic features as Ir is partially substituted by Ru or Ti. We find that for Ru substitution, $θ$ increases and stays negative, the anomaly in C$_{mag}$ is suppressed in magnitude and pushed to lower temperatures, low temperature $C \sim T^α$ with $α$ between $2$ and $3$ and decreasing towards $2$ with increasing $x$, and $T_f$ increases with increase in Ru concentration $x$. For Ti substitution we find that $θ$ and T$_f$ become smaller and the anomaly in $C_{mag}$ is completely suppressed. In addition, introducing non-magnetic Ti leads to the creation of orphan spins which show up in the low temperature magnetic susceptibility.

cond-mat.str-el↗

arXiv2018

Crystal growth and magnetic anisotropy in the spin-chain ruthenate Na$_2$RuO$_4$

We report single crystal growth, electrical resistivity $ρ$, anisotropic magnetic susceptibiltiy $χ$, and heat capacity $C_p$ measurements on the one-dimensional spin-chain ruthenate Na$_2$RuO$_4$. We observe variable range hopping (VRH) behaviour in $ρ(T)$. The magnetic susceptibility with magnetic field perpendicular ($χ_\perp$) and parallel ($χ_\parallel$) to the spin-chains is reported. The magnetic properties are anisotropic with $χ_\perp > χ_\parallel$ in the temperature range of measurements T $\approx 2$ to $305$ K with $χ_\perp / χ_\parallel$ $\approx 1.4$ at $305$ K. Analysis of the $χ(T)$ data reveals an anisotropy in the $g$-factor and Van-Vleck paramagnetic contribution. An anomaly in $χ(T)$ and a corresponding lambda-like anomaly in $C_p$ at $T_N = 37$ K confirms long-range antiferromagnetic ordering. This temperature is an order of magnitude smaller than the Weiss temperature $θ\sim -250$ K and points to suppression of long range magnetic order due to low dimensionality. However, we were unable to get a satisfactory fit of the experimental $χ(T)$ by an isolated one-dimensional spin-chain model, suggesting the importance of inter-chain interactions in Na$_2$RuO$_4$.

cond-mat.str-el↗

arXiv2017

Synthesis and pressure and field dependent magnetic properties of the Kagome-bilayer spin liquid Ca$_{10}$Cr$_7$O$_{28}$

We report synthesis of polycrystalline samples of the recently discovered spin liquid material Ca$_{10}$Cr$_7$O$_{28}$ and present measurements of the ambient and high pressure magnetic susceptibility $χ$ versus temperature $T$, magnetization $M$ versus magnetic field $H$ at various $T$, and heat capacity $C$ versus $T$ at various $H$. The ambient pressure magnetic measurements indicate the presence of both ferromagnetic and antiferromagnetic exchange interactions with dominant ferromagnetic interactions and with the largest magnetic energy scale $\sim 10$~K\@. The $χ(T)$ measurements under externally applied pressure of up to $P \approx 1$~GPa indicate the robust nature of the spin-liquid state despite relative increase in the ferromagnetic exchanges. $C(T)$ shows a broad anomaly at $T\approx 2.5$~K which moves to higher temperatures in a magnetic field. The evolution of the low temperature $C(T,H)$ and the magnetic entropy is consistent with frustrated magnetism in Ca$_{10}$Cr$_7$O$_{28}$.

cond-mat.str-el↗

arXiv2016

Spin liquid like Raman signatures in hyperkagome iridate Na$_4$Ir$_3$O$_8$

Combining Raman scattering measurements with mean field calculations of the Raman response we show that Kitaev-like magnetic exchange is dominant in the hyperkagome iridate Na$_4$Ir$_3$O$_8$. In the measurements we observe a broad Raman band at $\sim$~3500 cm$^{-1}$ with a band-width $\sim 1700$~cm$^{-1}$. Calculations of the Raman response of the Kitaev-Heisenberg model on the hyperkagome lattice shows that the experimental observations are consistent with calculated Raman response where Kitaev exchange interaction ($J_K$) is much larger than the Heisenberg term J$_1$ ($J_1/J_K \sim 0.1$). A comparison with the theoretical model gives an estimate of the Kitaev exchange interaction parameter.

cond-mat.str-el↗

arXiv2016

Raman Signatures of Strong Kitaev Exchange Correlations in (Na$_{1-x}$Li$_x$)$_2$IrO$_3$ : Experiments and Theory

Inelastic light scattering studies on single crystals of (Na$_{1-x}$Li$_x$)$_2$IrO$_3$ ($x = 0, 0.05$ and $0.15$) show a polarization independent broad band at $\sim $~2750 cm$^{-1}$ with a large band-width $\sim 1800$~cm$^{-1}$. For Na$_2$IrO$_3$ the broad band is seen for temperatures $ \leq 200$~K and persists inside the magnetically ordered state. For Li doped samples, the intensity of this mode increases, shifts to lower wave-numbers and persists to higher temperatures. Such a mode has recently been predicted (Knolle et.al.) as a signature of the Kitaev spin liquid. We assign the observation of the broad band to be a signature of strong Kitaev-exchange correlations. The fact that the broad band persists even inside the magnetically ordered state suggests that dynamically fluctuating moments survive even below $T_{N}$. This is further supported by our mean field calculations. The Raman response calculated in mean field theory shows that the broad band predicted for the spin liquid state survives in the magnetically ordered state near the zigzag-spin liquid phase boundary. A comparison with the theoretical model gives an estimate of the Kitaev exchange interaction parameter to be $J_K\approx 57$~meV.

cond-mat.str-el↗

arXiv2015

Evolution of magnetic, transport, and thermal properties in Na$_{4-x}$Ir$_3$O$_8$

The hyper-kagome material Na$_4$Ir$_3$O$_8$ is a three-dimensional spin-liquid candidate proximate to a quantum critical point (QCP). We present a comprehensive study of the structure, magnetic susceptibility $χ$, heat capacity $C$, and electrical transport on polycrystalline samples of the doped hyper-kagome material Na$_{4-x}$Ir$_3$O$_8$ ($x \approx 0, 0.1, 0.3, 0.7)$. Materials with $x\leq 0.3$ are found to be Mott insulators with strong antiferromagnetic interactions and no magnetic ordering down to $T = 2$ K\@. All samples show irreversibility below $T \approx 6$ K between the zero-field-cooled and field-cooled magnetization measured in low fields ($H = 0.050$ T) suggesting a frozen low temperature state although no corresponding anomaly is seen in the heat capacity. The $x = 0.7$ sample shows $ρ(T)$ which weakly increases with decreasing temperature $T$, nearly $T$ independent $χ$, a linear in $T$ contribution to the low temperature $C$, and a Wilson ratio $R_W \approx 7$ suggesting anomalous semi-metallic behavior.

cond-mat.str-el↗