  GdNi is a ferrimagnetic material with a Curie temperature Tc = 69 K which
exhibits a large magnetocaloric effect, making it useful for magnetic
refrigerator applications. We investigate the electronic structure of GdNi by
carrying out x-ray absorption spectroscopy (XAS) and x-ray magnetic circular
dichroism (XMCD) at T = 25 K in the ferrimagnetic phase. We analyze the Gd
M$_{4,5}$-edge ($3d$ - $4f$) and Ni L$_{2,3}$-edge ($2p$ - $3d$) spectra using
atomic multiplet and cluster model calculations, respectively. The atomic
multiplet calculation for Gd M$_{4,5}$-edge XAS indicates that Gd is trivalent
in GdNi, consistent with localized $4f$ states. On the other hand, a model
cluster calculation for Ni L$_{2,3}$-edge XAS shows that Ni is effectively
divalent in GdNi and strongly hybridized with nearest neighbour Gd states,
resulting in a $d$-electron count of 8.57. The Gd M$_{4,5}$-edge XMCD spectrum
is consistent with a ground state configuration of S = 7/2 and L=0. The Ni
L$_{2,3}$-edge XMCD results indicate that the antiferromagnetically aligned Ni
moments exhibit a small but finite magnetic moment ( $m_{tot}$ $\sim$ 0.12
$\mu_B$ ) with the ratio $m_{o}/m_{s}$ $\sim$ 0.11. Valence band hard x-ray
photoemission spectroscopy shows Ni $3d$ features at the Fermi level,
confirming a partially filled $3d$ band, while the Gd $4f$ states are at high
binding energies away from the Fermi level. The results indicate that the Ni
$3d$ band is not fully occupied and contradicts the charge-transfer model for
rare-earth based alloys. The obtained electronic parameters indicate that GdNi
is a strongly correlated charge transfer metal with the Ni on-site Coulomb
energy being much larger than the effective charge-transfer energy between the
Ni $3d$ and Gd $4f$ states.
