MAGNETIZATION IN CRYSTALS — DILLON 403 



which the magnetization lies in the plane. Here the application of 

 exceedingly small fields in the plane of the sample moves the inter- 

 vening 180° wall, and thus the total magnetization is very responsive 

 to the field. Hindrances to wall motion, such as actual holes in the 

 material, inclusions of some other compound, overall strain, or a small 

 highly strained region, modify this responsiveness very markedly. 

 All these effects can be seen in some degree in these transparent mag- 

 netic garnets. None of our samples ever becomes magnetically "hard" 

 in comparison with magnetoplumbite or ferroxdure. However, the 

 contrast between samples with one or more of the hindrances men- 

 tioned and samples in which the walls can move freely is very clear 

 and instructive. 



The transparency and magnetic rotation in the f errimagnetic garnets 

 enable us to see many of the characteristics of domain structure m 

 what are perhaps our best experimental magnetic specimens at this 

 time. From the point of view of demonstration and illustration, one 

 can see manifested in these domains and the way in which they behave 

 with field temperature, strain, etc., all the factors that determine the 

 magnetic behavior of a material, in addition to its own interest. The 

 ability to see the magnetization has proved to be a valuable tool in 

 fundamental magnetic research. 



REFERENCES 



1. Dillon, J. F., Jr. Optical properties of several ferrimagnetic garnets. 



Journ. Appl. Phys., vol. 29, pp. 539-541, 1958. 



2. Sheewood, R. C. ; Remeika, J. P. ; and Williams, H. J. Domain behavior in 



some transparent magnetic oxides. Journ. Appl. Phys., vol. 30, pp. 217- 

 225, 1959. 



3. Beetaut, F., and Foerat, F. Structure des ferrites ferrimagnetiques des 



terres rares. C.R. Acad. Sci. Paris, vol. 242, pp. 382-384, 1956. 



4. Gellee, S., and Gilleo, M. A. Structure and ferrimagnetism of yttrium and 



rare-earth iron garnets. Acta Crystallographica, vol. 10, p. 239, 1957. 

 4a. Gilleo, M. A., and Gellee, S. The interaction of magnetic ions in 

 GdaMn^GeiGaOio and related garnets. Journ. Phys. Chem. Solids, vol. 10, 

 pp. 187-190, 1959. 



5. Beetaut, F., and Pauthenet, R. Crystalline structure and magnetic prop- 



erties of ferrites having the general formula 5 FeaOs SM^Os. Proc. Inst. 

 Electr. Eng., B, vol. 104, suppl. 5, pp. 261-266, 1957. 



6. Nielsen, J. W., and Deaebobn, E. F. Growth of single crystals of magnetic 



garnets. Journ. Phys. Chem. Solids, vol. 5, pp. 202-207, 1958. 



7. Nielsen, J. W. Improved method for the growth of yttrium-iron and yttrium- 



gallium garnets. Journ. Appl. Phys., vol. 31, pp. 51S-52S, 1960. 



8. Lefever, R. a., and Chase, A. B. Substitutional incorporation of divalent 



iron into yttrium iron garnet. Journ. Chem. Phys., vol. 32, pp. 1575-1576, 

 1960. 



9. Dillon, J. F., Ja. Optical absorptions and rotations in the ferrimagnetic 



garnets. Journ. de Physique et le Radium, vol. 20, pp. 374-377, 1959. 

 10. Dillon, J. F., Je. Observation of domains in the ferrimagnetic garnets by 

 transmitted light. Journ. Appl. Phys., vol. 29, pp. 1286-1291, 1958. 



