Role of Ru vacancies in the magnetism of strain relaxed SrRuO_3 films on SrTiO_3 substrates

摘要

Magnetic properties of Ru-deficient strain relaxed SrRuO_3 films have been investigated. The ferromagnetic transitions drop off from 138 to 100 K with expansion of unit cell volume due to the Ru vacancies. A secondary transition starts appearing near to the bulk transition temperature of 155 K, indicating the two different Ru-deficient regions which result in an exchange structure. Anomalous variation of the saturation magnetization with the unit cell volume could be originated from the stabilization of the high spin Ru~(+4) states due to the Ru-vacancy and the induced crystal lattice distortions from cla > 1 to cla < 1.