High-field metamagnetism in the antiferromagnet ${\text{CeRh}}_2{\text{Si}}_2$

A study of the antiferromagnet ${\text{CeRh}}_2{\text{Si}}_2$ by torque, magnetostriction, and transport in pulsed magnetic fields up to 50 T and by thermal expansion in static fields up to 13 T is presented. The magnetic field temperature phase diagram of ${\text{CeRh}}_2{\text{Si}}_2$, where the magnetic field is applied along the easy axis $\mathbf{c}$, is deduced from these measurements. The second-order phase transition temperature $T_N$ and the first-order phase transition temperature $T_{1,2}$ ($=36\text{K}$ and 26 K at zero field, respectively) decrease with increasing field. The field-induced antiferromagnetic-to-paramagnetic borderline $H_c$, which equals 26 T at 1.5 K, goes from first order at low temperature to second order at high temperature. The magnetic field temperature phase diagram is found to be composed of (at least) three different antiferromagnetic phases. These are separated by the first-order lines $H_{1,2}$, corresponding to $T_{1,2}$ at $H=0$, and $H_{2,3}$, which equals 25.5 T at 1.5 K. A maximum of the $T^2$-coefficient $A$ of the resistivity is observed at the onset of the high-field polarized regime, which is interpreted as the signature of an enhanced effective mass at the field-induced quantum instability. The magnetic field dependence of the $A$ coefficient in ${\text{CeRh}}_2{\text{Si}}_2$ is compared with its pressure dependence, and also with the field dependence of $A$ in the prototypal heavy-fermion system ${\text{CeRu}}_2{\text{Si}}_2$.

Figure 1

(Color online) Magnetic field temperature phase diagram of ${\text{CeRh}}_2{\text{Si}}_2$, with $\mathbf{H}\parallel \mathbf{c}$, obtained from resistivity, torque, and thermal expansion. The inset focuses on the low-temperature part of the phase diagram.

Figure 2

(Color online) Thermal-expansion coefficient versus temperature of ${\text{CeRh}}_2{\text{Si}}_2$ measured for magnetic fields ${\mu }_{0}H=0$, 5, 10, and 13 T applied along $\mathbf{c}$.

Figure 3

Magnetic field dependence at $T=1.5\text{K}$ and for $\mathbf{H}\parallel \mathbf{c}$, (a) of the relative length $\Delta L_c/L_c$ of ${\text{CeRh}}_2{\text{Si}}_2$ and (b) of the related magnetostriction coefficient ${\lambda }_c$.

Figure 4

(Color online) Magnetic field derivative of the torque in ${\text{CeRh}}_2{\text{Si}}_2$ versus magnetic field for temperatures $T\le 24\text{K}$ and magnetic fields along $\mathbf{c}$.

Figure 5

(Color online) Resistivity ${\rho }_{xx}$ versus magnetic field $H$ in ${\text{CeRh}}_2{\text{Si}}_2$, for $\mathbf{H}\parallel \mathbf{c}$ and $1.5\le T\le 80\text{K}$.

Figure 6

(Color online) Magnetic field derivative of the resistivity $\partial {\rho }_{xx}/\partial \left({\mu }_{0}H\right)$ versus $H$ in ${\text{CeRh}}_2{\text{Si}}_2$ for $\mathbf{H}\parallel \mathbf{c}$ and $1.5\le T\le 36\text{K}$.

Figure 7

(Color online) Resistivity versus temperature ${\rho }_{xx}\left(T\right)$ of ${\text{CeRh}}_2{\text{Si}}_2$, for magnetic fields $\mathbf{H}\parallel \mathbf{c}$ of 0, 15, 25.5, 26.5, and 48 T.

Figure 8

(Color online) Resistivity of ${\text{CeRh}}_2{\text{Si}}_2$ in a ${\rho }_{xx}$ shown versus $T^2$, for $\mathbf{H}\parallel \mathbf{c}$ and (a) $H\le 25\text{T}$ and (b) $H\ge 25.5\text{T}$. Dotted lines correspond to fits to the data, for $T\le 8\text{K}$, by ${\rho }_{xx}={\rho }_{x,x}^0+A{T}^2$. (c) Plots of the quadratic coefficient $A$ (circles) and of the residual resistivity ${\rho }_{x,x}^0$ (rhombs) as a function of $H$. Red closed circles show the coefficient $A$ extracted for $H\ne H_c$ (where a quadratic fit sounds reasonable), while a red open circle is used for $A$ extracted at $H_c$ (where a quadratic fit is probably not justified). The errors bars come from the uncertainty in the numerical fits to the data. Red (full and dotted) lines are guides to the eyes for the field variation in $A$. The black line shows the field dependence of ${\rho }_{xx}$ measured at 1.5 K.

Figure 9

(Color online) Comparison of the magnetic field and pressure dependences (Refs. 8, 12) of the normalized quadratic coefficient $A/A_{\text{max}}$ of the low-temperature resistivity of ${\text{CeRh}}_2{\text{Si}}_2$ versus $\left(\delta -{\delta }^{\ast }\right)/\delta$. $\delta$ is the magnetic field or the pressure and ${\delta }^{\ast }$ its critical value.

Figure 10

(Color online) Schematic magnetic field pressure or doping-temperature phase diagram of the prototypal heavy-fermion system ${\text{CeRu}}_2{\text{Si}}_2$, when a magnetic field is applied along $\mathbf{c}$.

Figure 11

(Color online) Comparison of the magnetic field dependences of the quadratic coefficient $A$ of the low-temperature resistivity, in a $A/A_{\text{max}}$ versus $\left(H-H^{\ast }\right)/H$ plot, for the heavy fermions ${\text{CeRh}}_2{\text{Si}}_2$ and ${\text{CeRu}}_2{\text{Si}}_2$ (Ref. 27).