Increase of ferromagnetic ordering temperature by the minority-band double-exchange interaction in SrRu1-xCrxO3 -: art. no. 054428

Structural, magnetic, and resistive properties of the chromium substituted SrRu1-xCrxO3 perovskites with increased ferromagnetic transition temperature from 163 to 188 K were studied for polycrystalline samples synthesized in air and at high pressure. The Cr solubility limit found at x=0.15 in air is controlled by geometrical constraints of the tolerance factor and can be extended to higher values through high-pressure synthesis at 3 GPa. A linear decrease of the lattice parameters and bond lengths and an increase of the bond angles with x are consistent with the substitution of smaller Cr4+/3+ for Ru4+/5+. Similar decreases of the magnetic susceptibility chi(m) in the paramagnetic region above T-c and the high-field magnetization at 5 K with increasing x also indicate the presence of the Cr4+/3+ and Ru4+/5+ ions. This chemical substitution creates a possible Ru4+/5+(d(4/3))-O2--Cr4+/3+(d(2/3)) minority band double-exchange interaction which involves the Cr3+ and Cr4+ in magnetic ordering that enhances the ordering temperature. A reduced coercive field determined from the magnetization curves and a minimum of the resistivity point to decreased disorder for slightly substituted compositions x similar to 0.025.