Detecting magnetic spins on the nanoscale is useful as a step toward individually resolving such spins in magnetic imaging. The development of a single-spin resolution imaging technology poises itself on the brink of an age of new scientific advancement. Here we investigate using shallow nitrogen-vacancy (NV) center ensembles in diamond to detect nanoscale arrangements of gadolinium spins. We employ spin relaxometry techniques to determine if and where Gd³⁺ spins are present. Upon polarization, the characteristic time in which the NV returns to a thermal mixture of spin states is called T₁. Spin relaxometry operates on the principle that the T₁ measured on NVs goes down in the presence of strongly fluctuating magnetic fields. Gd³⁺ spins are chosen since they have a large spin S = 7/2 and thus produce such strongly fluctuating magnetic fields. We expect to detect T₁’s that are reduced by about an order of magnitude and demonstrate consistency with the regions of gadolinium deposition on the diamond surface. Informed by these results, we can move from ensemble measurement to measurement with a single NV, thus decreasing the spatial region over which Gd³⁺ spins can be detected and greatly improving the spatial resolution for imaging.