Surface Magnetic Anisotropic Energy Gap in Cu2O Nanoparticles

A weak surface magnetic anisotropy was observed in the thermal deviation of the saturation magnetization of Cu2O nanoparticles. The thermal deviation of the saturation magnetization is clearly a departure from the Bloch T3/2 law expected for isotropic systems, signaling the onset of magnetic anisotropy, and is presumably due to the high surface-to-volume ratio of the nanoparticles, and the surface atoms give rise to polarized moments. Here, we assume a uniaxial anisotropy and adopt the Heisenberg ferromagnet model for the applied magnetic field Ha-aligned moment-carrying Cu2O nanoparticles, and the surface magnetic anisotropic energy gap Δ can then be obtained from the fit, indicating that the anisotropic energy gap Δ can only be revealed at low temperatures.