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Surface induced magnetization reversal of MnP nanoclusters embedded in GaP

We investigate the quasi-static magnetic behavior of ensembles of non-interacting ferromagnetic nanoparticles consisting of MnP nanoclusters embedded in GaP(001) epilayers grown at 600, 650 and 700°C. We use a phenomenological model, in which surface effects are included, to reproduce the experimental hysteresis curves measured as a function of temperature (120-260 K) and direction of the applied field. The slope of the hysteresis curve during magnetization reversal is determined by the MnP nanoclusters size distribution, which is a function of the growth temperature. Our results show that the coercive field is very sensitive to the strength of the surface anisotropy, which reduces the energy barrier between the two states of opposite magnetization. Notably, this reduction in the energy barrier increases by a factor of 3 as the sample temperature is lowered from 260 to 120 K.