THE SPIN WAVE SPECTRA OF YTTRIUM- AND GADOLINIUM IRON GARNET
Abstract
The problem of deducing the values of the ex change integrals in yttrium- and gadolinium iron garnet from measurements of the magnetization and the magnetic contribution to the specific heat at low temperatures is considered. For these garnets the spin wave normal modes can be found by solving the semi-classical equations of motion which give rise to a set of n simultaneous linear equations, where n is the number of magnetically inequivalentions in the unit cell. Expressions for the thermodynamic functions at low temperatures in terms of the frequencies of the normal modes are given assuming the validity of the spin wave approximation. It is argued that the temperature variation of the frequency of these normal modes on the macroscopic properties can be completely accounted for without considering the zero point energy explicitly. Due to the size of the unit cell, the equations for the frequencies of the normal modes can only be solved numerically for general values of k. Such solutions are obtained for k lying along a (111) direction for various values of the exchange integrals, and the thermodynamic functions corresponding to these choices of parameters are calculated.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1963
- Accession Number
- AD0403661
Entities
People
- A. B. Harris
Organizations
- Duke University