Interface ferromagnetism in oxide superlattices of CaMnO3/CaRuO3

Abstract

Oxide superlattices composed of antiferromagnetic insulator layers of ${\mathrm{CaMnO}}_{\mathrm{3}}$ (10 unit cells) and paramagnetic metal layers of ${\mathrm{CaRuO}}_{\mathrm{3}}$ $\mathrm{(N}$ unit cells) were fabricated on ${\mathrm{LaAlO}}_{\mathrm{3}}$ substrates by pulsed-laser deposition. All the superlattices show ferromagnetic transitions at an almost identical temperature ${\mathrm{(T}}_C\text{∼95\hspace{0.17em}}\mathrm{K})$ and negative magnetoresistance below $T_C.$ Each magnetization and magnetoconductance of the whole superlattice at 5 K is constant and independent of ${\mathrm{CaRuO}}_{\mathrm{3}}$ layer thickness when normalized by the number of the interfaces between ${\mathrm{CaMnO}}_{\mathrm{3}}$ and ${\mathrm{CaRuO}}_{\mathrm{3}}.$ These results indicate that the ferromagnetism shows up only at the interface and is responsible for the magnetoresistance.