Surface spin-glass behavior in La2/3Sr1/3MnO3 nanoparticles

The low-temperature magnetic and transport properties of ${\mathrm{La}}_{\mathrm{2/3}}{\mathrm{Sr}}_{\mathrm{1/3}}{\mathrm{MnO}}_{\mathrm{3}}$ nanoparticles have been investigated. It is found that a surface spin-glass behavior exists in ${\mathrm{La}}_{\mathrm{2/3}}{\mathrm{Sr}}_{\mathrm{1/3}}{\mathrm{MnO}}_{\mathrm{3}}$ nanoparticles, which undergo a magnetic transition to a frozen state below 45 K. The low-temperature surface spin-glass behavior exists even at the highest field used $\text{(H=50\hspace{0.05em}}\mathrm{kOe}\mathrm{).}$ Moreover, the spin-glass-like transition disappears for particles above 50 nm. In addition, the suppressed low-field magnetoconductivity (LFMC) observed at low temperature for nanosized ${\mathrm{La}}_{\mathrm{2/3}}{\mathrm{Sr}}_{\mathrm{1/3}}{\mathrm{MnO}}_{\mathrm{3}}$ is obviously lower than the expected upper limit of LFMC, 1/3, for polycrystalline manganites, which is proposed to arise from the higher-order tunneling through the insulating spin-glass-like surface layers.