High-pressure phase of $\mathrm{CrS}{\mathrm{b}}_2$: A new quasi-one-dimensional itinerant magnet with competing interactions

We have synthesized the high-pressure form of $\mathrm{CrS}{\mathrm{b}}_2$ with $\mathrm{CuA}{\mathrm{l}}_2$-type structure under 7 GPa and 700 °C, and characterized its structural, transport, and magnetic properties by a suite of measurement techniques over a broad range of temperature, magnetic field, and pressure. In addition to previously reported ferromagnetic (FM) transition at $T_{\mathrm{C}}\approx 160$ K, we discover another antiferromagnetic spin-density-wave (SDW) transition at $T_{\mathrm{s}}\approx 90$ K, which is characterized by FM sheets of spins in the $ab$ plane that vary along the $c$ axis as determined by neutron powered diffraction. Pronounced anomalies around these two magnetic transitions are visible only in the lattice parameter $c$, signaling a strong spin-lattice coupling along the -Cr-Cr-Cr- infinite linear chain. We find that the application of magnetic field can suppress the SDW phase and stabilize the FM state down to the lowest temperature above ${\mu }_0{H}_{\mathrm{c}}\approx 3$ T, around which a peculiar non-Fermi-liquid behavior with reduced effective mass emerges. On the other hand, the application of high pressure induces complex evolution of the magnetic states, i.e., the FM order is lowered while the SDW order is enhanced quickly until they merge together into a single antiferromagnetic transition, which is suppressed completely at $P_{\mathrm{c}}\approx 9$ GPa. We observe near $P_{\mathrm{c}}$ non-Fermi-liquid behavior and enhancement of effective mass, which indicates the possible occurrence of magnetic quantum critical point. No superconductivity was observed down to 2 K around $P_{\mathrm{c}}$.

Figure 1

Observed (cross), calculated (solid line), difference (bottom line) profiles of the powder XRD patterns of the high-pressure form of $\mathrm{CrS}{\mathrm{b}}_2$ after Rietveld refinements. The inset shows the crystal structures viewed along different directions.

Figure 2

Physical properties of the high-pressure phase of $\mathrm{CrS}{\mathrm{b}}_2$. Temperature dependence of (a) magnetic susceptibility χ($T$) and its inverse, (b) resistivity ρ($T$) and its temperature derivative, (c) specific heat $C$($T$), and (d) thermopower $S$($T$) in the whole temperature range 2–300 K. Two magnetic transitions are marked by the vertical broken lines.

Figure 3

Determination of the magnetic structure of $\mathrm{CrS}{\mathrm{b}}_2$ using neutron powder diffraction. (a) A magnetic reflection develops around 160 K. (b) This can be described by ferromagnetic ordering with moments in the $ab$ plane. (c) Below 120 K a low-angle reflection is observed that alters position with temperature. (d) The low temperature magnetic structure is determined to be a spin density wave with a propagation vector that alters with temperature. The case for $\mathbf{k}=\left(0,0,1/5\right)$ is shown.

Figure 4

Temperature dependence of (a) lattice parameters $a$, $c$, and (b) volume $V$, and c/a ratio.

Figure 5

(a) Temperature dependence of magnetization $M$($T$) for $\mathrm{CrS}{\mathrm{b}}_2$ measured under different magnetic fields up to 7 T in both zero-field-cooled (ZFC) and field-cooled (FC) modes. (b) Isothermal magnetization curves $M$($H$) between +7 and −7 T at different temperatures.

Figure 6

(a) Temperature dependence of resistivity ρ($T$) of $\mathrm{CrS}{\mathrm{b}}_2$ measured under different magnetic fields up to 7 T. The magnetic transition temperatures $T_{\mathrm{C}}$ and $T_{\mathrm{s}}$ are determined from the peaks of dρ/dT curves shown on the top part of (a). (b) ρ vs $T^2$ plot of the low-temperature resistivity data.

Figure 7

Temperature-field phase diagram of $\mathrm{CrS}{\mathrm{b}}_2$. Field dependence of (a) $T_{\mathrm{C}}$, $T_{\mathrm{s}}$, and α, and (b) residual resistivity ${\rho }_0$ and $T$-quadratic coefficient $A$.

Figure 8

Temperature dependence of (a) DC magnetization $M$($T$) and (b) its derivative dM/dT under various hydrostatic pressures up to 0.9 GPa measured with the piston-cylinder cell in MPMS. (c) Field dependence of DC magnetization $M$($H$) measured at 10 K for different pressures. (d) Temperature dependence of AC magnetic susceptibility χ′($T$) under different hydrostatic pressures measured with a piston-cylinder cell.

Figure 9

Temperature dependence of resistivity ρ($T$) of $\mathrm{CrS}{\mathrm{b}}_2$ under various hydrostatic pressures up to 1.86 GPa measured with a self-clamped piston-cylinder cell. The top panel shows the temperature derivative curves dρ/dT.

Figure 10

Temperature dependence of resistivity ρ($T$) and its derivative dρ/dT of $\mathrm{CrS}{\mathrm{b}}_2$ under various hydrostatic pressures up to 8 GPa (a) and (b), and up to 11 GPa (c) and (d), measured with a palm cubic anvil cell. The top panels show the temperature derivative curves dρ/dT. (e) ρ vs $T^2$ plot of the low-temperature resistivity data of the S3 sample.

Figure 11

(a) Temperature-pressure phase diagram of $\mathrm{CrS}{\mathrm{b}}_2$. (b) Pressure dependencies of the resistivity exponent α and the $T$-quadratic coefficient $A$.