Monte Carlo simulation of magnetic properties in nanocrystalline-like systems

Those nanocrystalline materials which consist of ferromagnetic nanograins embedded in a ferromagnetic matrix were modelled as a cubic lattice composed of a central sphere with strongly coupled spins surrounded by weakly coupled spins. The magnetic behaviour was studied by Monte Carlo simulation, especially the low temperature spin ordering and features exhibited in the temperature range between the Curie temperatures of the two phases. The magnetization and magnetic susceptibility are calculated as a function of temperature for different values of the interfacial exchange interactions. It is shown that the exchange coupling between matrix and nanograin influences the magnetic properties of the nanograin, the matrix and the interfacial regions differently. The magnetic behaviour of different regions has been explained in terms of a polarization mechanism acting on the surface and in the core, leading to magnetic correlation between the spins. Such features are quite consistent with the experimental results obtained on nanocrystalline alloys.

[1]  B. Linder.  Phase Transitions and Critical Phenomena , 2005 .

[2]  J. Coey,et al.  Exchange coupling effects in nanocrystalline alloys studied by Monte Carlo simulation , 2002 .

[3]  J. Coey,et al.  Surface anisotropy in ferromagnetic nanoparticles , 2002 .

[4]  J. Kováč,et al.  Structural and magnetic properties of the intergranular amorphous phase in FeNbB nanocrystalline alloys , 2000 .

[5]  J. Greneche,et al.  Iron-based nanocrystalline alloys investigated by 57Fe Mössbauer spectrometry , 2000 .

[6]  J. Greneche,et al.  About the interfacial zone in nanocrystalline alloys , 2000 .

[7]  J. Greneche,et al.  Temperature dependence of amorphous and interface phases in the Fe80Nb7Cu1B12 nanocrystalline alloy , 1999 .

[8]  E. Tronc,et al.  Finite-size versus surface effects in nanoparticles , 1999, cond-mat/9910393.

[9]  J. Greneche,et al.  Hyperfine fields of amorphous residual and interface phases in FeMCuB nanocrystalline alloys: a Mössbauer effect study , 1999 .

[10]  R. Fischer,et al.  Magnetization processes in small particles and nanocrystalline materials , 1999 .

[11]  E. Tronc,et al.  Surface effects in nanoparticles: application to maghemite -Fe O , 1999, cond-mat/9903398.

[12]  R. Kodama,et al.  Atomic-scale magnetic modeling of oxide nanoparticles , 1999 .

[13]  J. Barandiaran,et al.  MODEL OF EXCHANGE-FIELD PENETRATION IN NANOCRYSTALLINE FE87ZR6B6CU ALLOYS FROM MAGNETIC AND MOSSBAUER STUDIES , 1998 .

[14]  Franck Carcenac,et al.  HIGH COERCIVITY IN ULTRATHIN EPITAXIAL MICROMETER-SIZED PARTICLES WITH IN-PLANE MAGNETIZATION : EXPERIMENT AND NUMERICAL SIMULATION , 1998 .

[15]  J. L. Breton,et al.  Structural properties of amorphous and nanocrystallized FeCuNbSiB and FeGdCuNbSiB ribbons , 1997 .

[16]  R. Fischer,et al.  Micromagnetism and the microstructure in nanocrystalline materials , 1997 .

[17]  J. Greneche,et al.  Magnetic interfaces in Fe-based nanocrystalline alloys determined by Mössbauer spectrometry , 1997 .

[18]  Kulik,et al.  Exchange interactions through amorphous paramagnetic layers in ferromagnetic nanocrystals. , 1994, Physical review. B, Condensed matter.

[19]  C. D. Gelatt,et al.  Optimization by Simulated Annealing , 1983, Science.

[20]  J. Cadogan,et al.  Random magnetocrystalline anisotropy in two-phase nanocrystalline systems , 1998 .