Physical properties of ${\mathrm{YbFe}}_5{\mathrm{P}}_3$ with a quasi-one-dimensional crystal structure

We report basic physical properties of the quasi-one-dimensional heavy-fermion compound $\mathrm{Yb}{\mathrm{Fe}}_5{\mathrm{P}}_3$. Its magnetic susceptibility follows a modified Curie-Weiss behavior at high temperatures with a Weiss temperature between $-5$ and $-21$ K depending on the direction of the applied magnetic field. Our single crystals of $\mathrm{Yb}{\mathrm{Fe}}_5{\mathrm{P}}_3$ are good metals with a room-temperature resistivity of $\sim 140$ $\mu \mathrm{\Omega }$ cm and a residual resistivity of less than 2 $\mu \mathrm{\Omega }$ cm. Below $\sim 2$ K the resistivity reflects the presence of strong quantum fluctuations, which is supported by specific heat measurements that show a similar strong enhancement in $C/T$ at low temperatures reaching 1.5 J/mol ${\mathrm{K}}^2$ below $T=0.5$ K. No magnetic ordering is observed down to 80 mK. Magnetic fields up to 8 T rapidly suppress the magnetic fluctuations, while resistivity measurements under pressures up to 2.54 GPa indicate the enhancement of quantum fluctuations, although still no order is observed down to 0.3 K. Density functional theory calculations suggest the presence of electronically quasi-one-dimensional (1D) Fermi surface sheets together with three-dimensional electronic pockets. We suggest that the quasi-1D nature of this compound leads to an extended regime of large quantum fluctuations within the paramagnetic state prior to reaching a magnetic instability.

Figure 1

Crystal structure of $\mathrm{Yb}{\mathrm{Fe}}_5{\mathrm{P}}_3$. (a) Viewed down the $b$ axis, the chain direction. The big red spheres indicate the position of Yb atoms. Medium brown spheres depict iron, and small purple spheres are for P. The dashed square indicates the unit cell. The solid lines show the nearest bonds between Fe and P atoms. (b) Viewed from the $c$ axis. Vertical lines between Yb atoms indicate the nearest Yb-Yb distance along the chain direction, 0.365 nm.

Figure 2

(a) Magnetic susceptibility $\chi$ as a function of temperature for field along the $a$ (green up-pointing triangles), $b$ (red circles), and $c$ axes (blue down-pointing triangles). Inset: The modified Curie-Weiss plot 1/($\chi -{\chi }_0$), where ${\chi }_0=0.0029,0.0039$, and 0.0029 emu/mol for $H\parallel a, b$, and $c$, respectively. The magnetic moment and Curie-Weiss temperatures from the fits to the modified Curie-Weiss law are reported in the inset. (b) Magnetic field dependence of magnetization with $H\parallel a$ (green up-pointing triangles), $H\parallel b$ (red circles), and $H\parallel c$ (blue down-pointing triangles). The data were taken at $T=2$ K.

Figure 3

(a) The temperature dependence of resistivity along the chain direction. A magnetic field of $H=0.2$ T was applied to suppress the superconductivity from an impurity. Insets: The expanded data between $T=0$ and 40 K (lower right) and between 0 and 1 K (upper left). (c) Transverse resistivity ${\rho }_{xy}$ versus temperature. A magnetic field of $H=\pm 2$ T was applied perpendicular to the chain direction and the data are antisymmetrized.

Figure 4

Specific heat divided by temperature, $C/T$, as a function of temperature at low temperatures for $\mathrm{Yb}{\mathrm{Fe}}_5{\mathrm{P}}_3$ (red squares) and $\mathrm{Lu}{\mathrm{Fe}}_5{\mathrm{P}}_3$ (blue circles). An upturn below $T=0.2$ K originates from the nuclear Schottky anomaly. Inset: Entropy of $\mathrm{Yb}{\mathrm{Fe}}_5{\mathrm{P}}_3$ versus temperature. The dashed line shows $Rln2=5.76$ J/mol K.

Figure 5

DFT computed Fermi surfaces of $\mathrm{Yb}{\mathrm{Fe}}_5{\mathrm{P}}_3$ for (a) the itinerant configuration and (b) the localized configuration of the $f$ electron. Different colors are used to simply distinguish different Fermi surface sheets.

Figure 6

(a) Specific heat divided by temperature, $C/T$, versus temperature at different magnetic fields applied parallel to the $b$ axis. The nuclear Schottky contribution $C_{\mathrm{nuc}}$ has been subtracted from the data as described in the text. (b) $C/T$ at different magnetic fields applied parallel to the $c$ axis. (c) Resistivity $\rho$ versus temperature at different magnetic fields applied parallel to the $c$ axis showing the suppression of the non-Fermi-liquid behavior with fields. The solid lines are quadratic fits to the form $\rho \left(T\right)$ = ${\rho }_0 + A{T}^2$ between the base temperature and 1.5 K. $A$ is 0.626 and 0.467 $\mu \mathrm{\Omega }\mathrm{cm}/{\mathrm{K}}^2$ for 5 and 8 T, respectively. Arrows indicate the position where the resistivity starts to deviate from the quadratic curves.

Figure 7

(a) The pressure dependence of resistivity $\rho$ versus temperature from $P=0$ to 2.2 GPa. (b) An expanded view of the pressure-dependent resistivity data between $T=0$ and 3 K for selected pressures 0 (black circles), 0.97 (blue triangles), and 2.54 (red squares) GPa. Solid lines are linear fits to $\rho \left(T\right)$=${\rho }_0 + BT$ at low temperatures. Arrows indicate where $\rho$ deviates from the linear behavior. Inset: The slope of the linear fitting parameter $B$ as a function of pressure.