de Haas–van Alphen Effect Across the Metamagnetic Transition in ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$

We report a study of the de Haas–van Alphen (dHvA) effect on the itinerant metamagnet ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$. Extremely high sample purity allows the observation of dHvA oscillations both above and below the metamagnetic transition field of 7.9 T. The quasiparticle masses are fairly large away from the transition, and are enhanced by up to an extra factor of 3 as the transition is approached, but the Fermi surface topography change is quite small. The results are qualitatively consistent with a field-induced Stoner transition in which the mass enhancement is the result of critical fluctuations.

Figure 1

The real part of the differential magnetic susceptibility through the metamagnetic transition in ${\mathrm{Sr}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$. The ordinates are on a logarithmic scale, while the abscissae are on a reciprocal scale since quantum oscillations are periodic in reciprocal field. The oscillations are seen below (red) and above (blue) the transition, but are almost indistinguishable on a linear ordinate scale (inset).

Figure 2

The Fourier transformation of the oscillatory data of Fig. 1. The color coding corresponds to that of Fig. 1: red and blue for below and above the transition, respectively. The transformations were performed over the regions $5.5\mathrm{T}<B<6.5\mathrm{T}$ and $10\mathrm{T}<B<15\mathrm{T}$, where the frequency is field independent (see inset). The inset shows the field dependence of the main peak frequency below and above the transition (1.8 and 1.6 kT, respectively).

Figure 3

Effective mass as a function of field for the peaks at 1.8(6) and 4.2(0) kT for the low-field (high-field) states. The dotted lines are guides to the eye. The pronounced increase in the effective mass of the Landau quasiparticles can be understood in terms of fluctuations close to a quantum critical point.