Contactless measurements of Shubnikov-de Haas oscillations in the magnetically ordered state of $\mathrm{Ce}\mathrm{Ag}{\mathrm{Sb}}_2$ and $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ single crystals

Shubnikov-de Haas oscillations were measured in single crystals of highly metallic antiferromagnetic $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ and ferromagnetic $\mathrm{Ce}\mathrm{Ag}{\mathrm{Sb}}_2$ using a tunnel diode resonator. Resistivity oscillations as a function of applied magnetic field were observed via measurements of skin depth variation. The effective resolution of $\Delta \rho \simeq 20\mathrm{p}\Omega$ allows a detailed study of the SdH spectra as a function of temperature. The effects of the Sm long-range magnetic ordering as well as its electronic structure ($4f$ electrons) on the Fermi surface topology is discussed.

Figure 1

(Color online) Optical images of studied crystals. (a) $\mathrm{Ce}\mathrm{Ag}{\mathrm{Sb}}_2$ and (b) $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$. Each crystal was $0.7\times 0.7\times 0.3{\mathrm{mm}}^3$.

Figure 2

(Color online) Resistivity versus temperature for $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ single crystal measured directly (open symbols) and inferred from the skin depth measurements (solid line). The inset shows variation of the skin depth with temperature.

Figure 3

(Color online) Relative frequency shift in a magnetic field for $\mathrm{Ce}\mathrm{Ag}{\mathrm{Sb}}_2$ (top) and $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ (bottom) at $1.8\mathrm{K}$.

Figure 4

(Color online) Oscillations of the reconstructed resistivity versus reciprocal magnetic field in $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ single crystal measured at several temperatures below $T_c$. The curves are offset for clarity.

Figure 5

(Color online) Power spectra of Shubnikov-de Haas oscillations obtained from the data shown in Fig. 4. The curves are offset for clarity.

Figure 6

(Color online) Low-frequency portion of the power spectra of Shubnikov-de Haas oscillations measured in $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ at $T=0.5\mathrm{K}$.

Figure 7

(Color online) Temperature dependence of $\beta$ and ${\gamma }^{\prime }$ peaks power spectrum amplitudes in $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$. Inset: log of Fourier transform amplitude over $T$—used in calculation of the effective mass.

Figure 8

(Color online) Shubnikov-de Haas oscillations (raw data in terms of the resonant frequency shift) in single crystal $\mathrm{Ce}\mathrm{Ag}{\mathrm{Sb}}_2$ measured at indicated temperatures. The curves are offset for clarity.

Figure 9

(Color online) Power spectra of Shubnikov-de Haas oscillations observed in $\mathrm{Ce}\mathrm{Ag}{\mathrm{Sb}}_2$ single crystal. The curves are offset for clarity.

Figure 10

(Color online) Band structure of $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ calculated from ASA TBLMTO. $E_F$ corresponds to zero energy. The nonmagnetic result is shown by the solid lines; the antiferromagnetic case is shown by the dotted lines.

Figure 11

(Color online) Fermi surface of $\mathrm{Sm}\mathrm{Ag}{\mathrm{Sb}}_2$ corresponding to (a) band 1, (b) band 2, and (c) band 3. The extremal orbits indicated by greek letters and shown by arrows.