Energy barrier enhancement by weak magnetic interactions in Co/Nb granular films assembled by inert gas condensation

A series of nanogranular Co/Nb samples has been prepared using an unfiltered beam of Co nanoparticles preformed by inert gas condensation. The preparation technique is shown to be a simple and effective method for fabricating, in a single deposition step, a sample series across which both particle size and concentration vary. We estimate the presence of weak interparticle (dipole-dipole) interactions ranging from 7 to 19% in strength (normalized to the median anisotropy energy barrier) across the present series. With the aim of elucidating the effect of such interactions on the blocking behavior of such nanogranular material, we have studied the field and temperature dependence of the magnetization in the films. For each sample, the temperature of the maximum in the zero-field-cooled magnetization curve (TMAX) is found to lie between the values of blocking (TB )a nd freezing (TF) temperature estimated from the experimentally determined particle size and concentration; i.e., TB

Keywords:

• Nanoparticle
• Particle
• Condensed matter physics
• Nuclear magnetic resonance
• Anisotropy energy
• Anisotropy
• Inert gas
• Condensation
• Physics
• Magnetization
• Particle size

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