  Magnetic susceptibility of elemental copper (Cu) shows an anomalous rise at
low temperatures superimposed on the expected atypical diamagnetic response.
Such temperature dependent susceptibility, which is also known as the Curie
tail, can not be explained on the basis of Larmor diamagnetic and Pauli
paramagnetic contributions expected in Cu. Using valence band resonant
photoemission spectroscopy results and density functional theory calculations,
we show the magnetic anomaly appears due to presence of holes in Cu 3d band,
which originates from thermally excited electronic configuration. Our study
therefore highlights that the Curie tail, which is generally overlooked
presuming it either due to paramagnetic impurities or defects, can in fact be
intrinsic to a material, and even simple systems like elemental Cu is
susceptible to electronic excitations giving rise to anomalous magnetic state.
