A theoretical study on size-dependent magnetic properties of Gd particles in the 4–300K temperature range

Abstract We present a statistical thermodynamical study on the effect of varying the size of spherical particles of Gd (8–160 A in radius) on their magnetic properties in the temperature range 4–300 K. The energy density of the system is the sum of the magnetic anisotropy, Zeeman and demagnetization energies.The magnetization and magnetic susceptibility dependencies on field, temperature and size are calculated from the partition function. Particles in the 8–30 A size range show magnetic properties different from those of larger particles. The smallest particles, in this range, show evidence of superparamagnetic behavior.