Unconventional Metallic Magnetism in ${\mathrm{L}\mathrm{a}\mathrm{C}\mathrm{r}\mathrm{S}\mathrm{b}}_3$

Neutron-diffraction measurements in ${\mathrm{L}\mathrm{a}\mathrm{C}\mathrm{r}\mathrm{S}\mathrm{b}}_3$ show a coexistence of ferromagnetic and antiferromagnetic sublattices below $T_C=126\mathrm{K}$, with ordered moments of 1.65(4) and $0.49(4){\mu }_B/\mathrm{\text{formula unit}}$, respectively ($T=10\mathrm{K}$), and a spin-reorientation transition at $\approx 95\mathrm{K}$. No clear peak or step was observed in the specific heat at $T_C$. Coexisting localized and itinerant spins are suggested.

Figure 1

(a) Crystal structure of ${\mathrm{L}\mathrm{a}\mathrm{C}\mathrm{r}\mathrm{S}\mathrm{b}}_3$. (b) Projection of the Cr sublattice onto the $\mathbf{b}\mathbf{c}$ plane. The arrows represent the Cr magnetic structures in this compound below 95 K ($T_{\mathrm{s}\mathrm{r}}$) and between $T_{\mathrm{s}\mathrm{r}}$ and 126 K ($T_C$). The angle between neighboring spins, $\alpha =36(4)°$, is the same within experimental error for both $T$ intervals.

Figure 2

(a)–(c) $T$ dependence of the intensities of selected Bragg reflections: (100) (a), (020) and (002) (b), and (001) (c). The solid line in (a) is a fit to a power law. The dashed line in (b) is a guide to the eyes. The vertical dotted lines mark the spin-reorientation ($T_{\mathrm{s}\mathrm{r}}$) and long-range magnetic ordering ($T_C$) transition temperatures. (d)–(f) Magnetic-field dependence of the intensity of (100) (d), (002) (e), and (001) (f) reflections at 100 K, taken with increasing field (filled symbols), and with decreasing field after the application of 0.035 T [open symbols in (f)]. The field was applied along $\mathbf{b}$.

Figure 3

$T$ dependence of the $dc$ magnetization (open symbols) and zero-field specific heat, $C(T)$ (filled symbols), measured for the same crystal of ${\mathrm{L}\mathrm{a}\mathrm{C}\mathrm{r}\mathrm{S}\mathrm{b}}_3$. The magnetization was measured under an applied magnetic field of 0.1 T along $\mathbf{b}$. The solid line is a simulation for the magnetic contribution to $C(T)$ (see text).