Anisotropy of the low-temperature magnetostriction of Sr3Ru2O7

We use high-resolution capacitive dilatometry to study the low-temperature linear magnetostriction of the bilayer ruthenate Sr3Ru2O7 as a function of magnetic field applied perpendicular to the ruthenium-oxide planes (B parallel to c). The relative length change Delta L(B)/L is detected either parallel or perpendicular to the c-axis close to the metamagnetic region near B = 8 T. In both cases, clear peaks in the coefficient lambda(B) = d(Delta L/L)/dB at three subsequent metamagnetic transitions are observed. For Delta L perpendicular to c, the third transition at 8.1 T bifurcates at temperatures below 0.5 K. This is ascribed to the effect of an in-plane uniaxial pressure of about 15 bar, unavoidable in the dilatometer, which breaks the original fourfold in-plane symmetry.