LOCALIZED MAGNONS IN FERROMAGNET WITH IMPURITY SPIN .I.

The energies of the localized magnons around an impurity spin in a linear chain of ferromagnet in the case of S = S ′=1/2 were calculated, where S and S′are the magnitude of the host and impurity spin, respectively. Two types of the localized magnons were obtained; one is the s type which is the energy of the ground state when the impurity spin couples antiferromagnetically with its nearest neighboring host spins, and it is already obtained by Wang and Callen, and the other is the p type. An approximate method to get the ground state for S ′≥1 is proposed. The energies of the two localized magnons were calculated by solving approximately the Dyson equation for Green functions. The spin wave method by Ishii, Kanamori and Nakamura is discussed. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.