Negative Magnetization Induced By Particle-Size Reduction In Gd1-Xcaxmno3 Nanoparticle Systems

We report a pervasive phenomenon of gradual emergence of negative magnetization in typical R1-xDxMnO3 orthorhombic perovskite manganites in nanoform (with R3+ being a trivalent high-magnetic-moment ion from the heavier rare-earth elements Gd, Tb, Dy and D2+ refers to divalent alkaline elements Sr, Ca, etc.), while the bulk form manifests no negative magnetization. Extensive magnetization studies have been carried out in Gd1-xCaxMnO3 around half doping. We demonstrate experimentally that particle size reduction in nano-form manganites enhances the propensity of the system to exhibit negative magnetization and propose a theoretical explanation for the phenomenon. To test the universality of our findings, we have extended the measurement to Dy0.6Ca0.4MnO3 and obtained similar results.