Dependence of the Effective Masses in ${\mathrm{Y}\mathrm{b}\mathrm{A}\mathrm{l}}_3$ on Magnetic Field and Disorder

The susceptibility and specific heat—and hence the effective mass—of the intermediate valence compound ${\mathrm{Y}\mathrm{b}\mathrm{A}\mathrm{l}}_3$ show anomalous enhancement below the Fermi liquid temperature $T_{\mathrm{c}\mathrm{o}\mathrm{h}}\sim 40\mathrm{K}$. We show that these anomalies are suppressed by alloying in ${\mathrm{Y}\mathrm{b}}_{1-x}{\mathrm{L}\mathrm{u}}_x{\mathrm{A}\mathrm{l}}_3$ indicating high sensitivity to lattice coherence. The de Haas–van Alphen effective masses for key branches of the Fermi surface are reduced by magnetic fields $B>40\mathrm{T}$. We argue that this reduction does not arise from $4f$ polarization but reflects renormalization of the quasiparticle states by the field.

Figure 1

(a) The susceptibility and (b) the specific heat coefficient for ${\mathrm{Y}\mathrm{b}}_{1-x}{\mathrm{L}\mathrm{u}}_x{\mathrm{A}\mathrm{l}}_3$. (Symbols for different $x$ are the same in both panels.) The inset compares the susceptibility of ${\mathrm{Y}\mathrm{b}\mathrm{A}\mathrm{l}}_3$ in low and high magnetic fields (Ref. 2).

Figure 2

The de Haas–van Alphen frequencies of ${\mathrm{Y}\mathrm{b}\mathrm{A}\mathrm{l}}_3$ as a function of angle with respect to the high symmetry directions. The different symbols correspond to different field ranges for the measurement.

Figure 3

(a) The fast Fourier transform of the de Haas–van Alphen spectrum at 0.84 K for a field along the $⟨111⟩$ direction for fields in the range $45\le B\le 55\mathrm{T}$. (b) A mass plot and (c) a Dingle plot for the $\alpha$ and $\beta$ branches for a field along $⟨111⟩$. (See text for the fitting function.)

Figure 4

The dHvA masses in units of the free electron mass $m_e$ for different branches of the Fermi surface of ${\mathrm{Y}\mathrm{b}\mathrm{A}\mathrm{l}}_3$ as a function of magnetic field for (a) and (b) fields along the $⟨111⟩$ direction and (c) field along the $⟨100⟩$ direction. A large reduction of the $\alpha$ and $\beta$ branches is observed at high field. Inset: The field dependence of the magnetic susceptibility, showing that $\chi (B)$ decreases for $B>40\mathrm{T}$.