Magnetic field and pressure tuning of the heavy fermion antiferromagnet CePdIn

TL;DR

CePdIn is used to study how geometric frustration and Kondo screening compete to set magnetic order in a heavy-fermion system. The authors map magnetic-field and hydrostatic-pressure phase diagrams, revealing a non-monotonic evolution of $T_{ m N}$ with pressure and the existence of two distinct AF phases AF$_1$ and AF$_2$ separated near $p \approx 2.6$ GPa, with AF$_2$ more robust against field due to a likely change in the electronic state driven by enhanced Kondo hybridization. The data also show merging of resistivity maxima and a crossover to a more degenerate Kondo state under pressure. Overall, the work demonstrates how reduced frustration and dimensionality in CePdIn tune quantum critical behavior within the ZrNiAl-type family, offering a pathway to control frustration in metallic Kondo lattices.

Abstract

Frustrated Kondo lattices are ideal platforms for studying how both the Kondo effect and quantum fluctuations compete with the magnetic exchange interactions that drive magnetic ordering. Here, we investigate the effect of tuning the heavy-fermion compound CePdIn, which crystallizes in the geometrically frustrated ZrNiAl-type structure, using applied magnetic fields and hydrostatic pressure. At ambient pressure, CePdIn exhibits two magnetic transitions, one at $T_{\rm{N}} \approx 1.65$ K and another at $T_{\rm{M}} \approx 1.15$ K, which are both suppressed by applied $c$-axis fields. Upon applying pressure in zero magnetic field, there is a non-monotonic evolution of $T_{\rm{N}}$, which decreases to 0.8 K at 2.3 GPa, before abruptly increasing to 1.5 K at 2.6 GPa. At higher pressures, $T_{\rm{N}}$ has a weak pressure dependence, and vanishes near 5 GPa. Together with the high-pressure phase being more robust to applied fields, these results suggest two distinct antiferromagnetic phases in CePdIn, which are separated near 2.6 GPa, and this change may be driven by the evolution of the underlying electronic structure due to enhanced Kondo hybridization under pressure.

Figures (11)

• Figure 1: Isothermal magnetization versus applied field $M(H)$ of CePdIn at (a) 0.1 K for magnetic fields along and perpendicular to the $c$-axis, as well as at (b) 0.4 K, and (c) 1.2 K for magnetic fields along the $c$-axis. The solid lines in (b) and (c) are the field derivatives of $M(H)$. Arrows in (a) indicate whether the measurement was performed upon increasing or decreasing the field. Arrow in (b) indicates the metamagnetic transition $H_{\rm{M}}$.
• Figure 2: Temperature dependence of the resistivity $\rho(T)$ of CePdIn with the current applied parallel and perpendicular to the $c$-axis. The arrows indicates the temperature corresponding to the resistivity maxima.
• Figure 3: (a) Temperature dependence of the resistivity $\rho(T)$ and its temperature derivative d$\rho(T)$/d$T$ with the current applied perpendicular to the $c$-axis. The arrows mark the two transitions at $T_{\rm{N}}$ and $T_{\rm{M}}$. (b) Temperature dependence of the specific heat as $C(T)/T$ of CePdIn and LaPdIn. The inset displays a plot of $C/T$ versus $T^2$, and the solid line represents a linear fit.
• Figure 4: (a) Temperature dependence of the magnetic contribution to the specific heat as $C_{\rm{m}}(T)/T$ on a logarithmic temperature scale, with various magnetic fields applied along the $c$-axis. The inset shows the temperature dependence of the magnetic entropy $S_{\rm{m}}/(T)$ at various magnetic fields. (b) Temperature dependence of the resistivity $\rho(T)$ in various applied $c$-axis magnetic fields. The dashed lines correspond to fitting with Fermi liquid behavior. (c) Temperature derivative of the resistivity d$\rho(T)$/d$T$ in various applied $c$-axis magnetic fields. The black arrows in (a) and (c) highlight the evolution of the transition temperatures $T_{\rm{N}}$ and $T_{\rm{M}}$ with field, and the red arrow in (a) marks the hump temperature $T_{\rm{max}}$ in the heat capacity.
• Figure 5: Magnetic field-temperature phase diagram of CePdIn for magnetic fields applied along the $c$-axis deduced from heat capacity, resistivity, and magnetization measurement. The vertical light gray line indicates the boundary between the antiferromagnetic state and the paramagnetic state. Error bars correspond to transition widths.