Structural, electronic, and magnetic properties of HoCo${}_2$ thin films grown by pulsed laser deposition

We report the growth and physical properties of HoCo${}_2$ thin films on Si substrate by pulsed laser deposition. Well-defined Kiessig fringes in the x-ray reflectivity data yield a film thickness of $35\pm 1$~nm and demonstrate smooth film surface and interface profiles. Atomic force microscopy confirms the high morphological quality of the films, revealing subnanometer surface roughness of $\sim$170~pm. Two independently prepared films exhibit a reproducible ferrimagnetic transition at $T_{\mathrm{C}}=77\pm 3$~K, demonstrating retention of the characteristic magnetic ordering of bulk HoCo${}_2$. However, the absence of resolvable thermal hysteresis indicates a predominantly continuous, second-order like transition in the films, in contrast to the first-order transition of bulk HoCo${}_2$. At 5~K, the films exhibit clear magnetic hysteresis with a coercive field of $\sim$600~Oe, substantially larger than the negligible coercivity of bulk HoCo${}_2$. X-ray photoelectron spectroscopy reveals comparable Ho $4d$ and Co $2p$ core-level line shapes and broadly similar valence-band spectra for the bulk and film, indicating preservation of the essential local electronic environment and occupied electronic structure.