Size-dependent nonmagnetic surface layer of ferromagnetic nanoparticles.
Based on the size-dependent melting temperature, we have deduced the analytic models for size-dependent Curie temperature Tc and saturation magnetization at room temperature Ms for ferromagnetic nanocrystals. The Tc(D) and Ms(D) functions decrease with decreasing size D. Agreements between model predictions and the corresponding experimental results enable us to determine the size-dependent thickness of nonmagnetic surface layer phi(D) and lambda(D) in describing Tc(D) and Ms(D), respectively. It is found that the surface layer should be an intrinsic property of ferromagnetic crystals since the nonmagnetic surface layer exists in the whole size range rather than vanishes as D approaches infinite.
National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, P. R. China.
Haiming
H
Lu
Xiangkang
X
Meng