Measuring the penetration depth anisotropy in Mg B2 using small-angle neutron scattering

Using small-angle neutron scattering, we have measured the misalignment between an applied field of 4 kOe and the flux-line lattice in Mg B2, as the field is rotated away from the c axis by an angle θ. The measurements, performed at 4.9 K, showed the vortices canting towards the c axis for all field orientations. Using a two-band/two-gap model to calculate the magnetization, we are able to fit our results yielding a penetration depth anisotropy, γλ =1.1±0.1.