THEORY OF MAGNETICALLY DILUTE SYSTEMS

The variation of the critical temperature (the Curie or Néel temperature) of a magnetic crystal randomly diluted with non-magnetic atoms is evaluated as a function of concentration ρ of magnetic atoms by the effective Hamiltonian method based on the Ising and the Heisenberg models. The specific heat of Ising ferromagnet above the Curie temperature is calculated for various concentrations in order to see the existence of Schottky-type maximum. The critical index of susceptibility and the Curie temperature for diluted ferromagnet is also calculated using Padé approximation to check the idea that the lowering of the Curie temperature with the decrease of ρ is attributed to the decrease of effective dimensionality of ferromagnetic system. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.