Growth and morphological evolution of Co_3-xMn_xO₄ (x = 1, 2) thin films

We grew epitaxial CoMn₂O₄ and Co₂MnO₄ thin films on Nb doped (0.1 wt.%) SrTiO₃(100) single crystal substrates by using pulsed laser deposition and studied how the growth temperature affected their crystal structures and surface morphologies. For Co₂MnO₄, increasing the growth temperature induced no significant changes except for an enlarged grain size. In contrast for CoMn₂O₄, increasing the growth temperature caused its surface morphology to evolve from spherical grains to rectangular nanorods; additionally, X-ray diffraction showed that these rectangular nanorod grains scattered to domains with different crystal orientations. We attribute this rectangular nanorod pattern to self-assembled domains originating from Jahn-Teller distortions and film-substrate lattice mismatch.