Thickness Dependence of Magnetic and Transport Properties of Chromium Dioxide (CrO2) Strained Epitaxial Thin Films

Chromium dioxide (CrO2) thin films of different thicknesses (120–2600 A) have been grown epitaxially on (100)-oriented TiO2 substrates by the chemical vapor deposition technique. The thicker films, with a Curie temperature of 395 K, exhibit in-plane magnetocrystalline anisotropy with the magnetic easy axis along the -axis direction. At low temperatures, the easy axis is deflected from the toward the -axis in the thickness range 1500–600 A. For even smaller thicknesses, the -axis and the magnetic easy axis coincide again. However, at 300 K, the -axis is always the magnetic easy axis in every film studied. Resistivity measurement in the temperature range of 4.2 to 420 K has also been performed. Temperature dependence of the resistivity is highly anisotropic between the and the -axis, due to thickness induced anisotropic strain in the CrO2 films.