EXCHANGE STIFFNESS OF CA-DOPED YIG

Authors
Citation
I. Avgin et Dl. Huber, EXCHANGE STIFFNESS OF CA-DOPED YIG, Journal of applied physics, 75(10), 1994, pp. 5517-5519
Citations number
9
Categorie Soggetti
Physics, Applied
Journal title
ISSN journal
00218979
Volume
75
Issue
10
Year of publication
1994
Part
2A
Pages
5517 - 5519
Database
ISI
SICI code
0021-8979(1994)75:10<5517:ESOCY>2.0.ZU;2-S
Abstract
An effective medium theory for the zero-temperature exchange stiffness of uncompensated Ca-doped YIG is presented. The theory is based on th e assumption that the effect of the Ca impurities is to produce strong , random ferromagnetic interactions between spins on the a and d subla ttices. In the simplest version of the theory, a fraction, x, of the a d exchange integrals are large and positive, x being related to the Ca concentration. The stiffness is calculated as function of x for arbit rary perturbed ad exchange integral, J(ad)x. For J(ad)x > (1/5)18J(aa) + 3J(dd)\, with J(aa) and J(dd) denoting the aa and dd exchange integ rals, respectively, there is a critical concentration, X(c), such that when x>X(c), the stiffness is complex. It is suggested that X, deline ates the region where there are significant departures from colinearit y in the ground state of the Fe spins. Extension of the theory to a mo del where the Ca doping is assumed to generate Fe4+ ions on the tetrah edral sites is discussed. Possible experimental tests of the theory ar e mentioned.