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XIV.—On a Sensitive State induced in Magnetic Materials by Thermal Treatment.

Published online by Cambridge University Press:  15 September 2014

James G. Gray  and
Alexander D. Ross
James G. Gray
Affiliation:
University of Glasgow
Alexander D. Ross
Affiliation:
University of Glasgow
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Summary

1. Specimens of steel cooled from high temperatures are, as regards their magnetic properties, in a “sensitive state.”

2. After magnetisation, reversal of the field reduces the susceptibility.

3. Cyclic reversals of the field between definite limits bring the magnetic quality to a definite lower value for fields lying between these limits.

4. So long as the field is not changed in sign, the “sensitive state” persists.

5. Cyclic reversals of the field between narrow limits reduce the susceptibility for fields beyond these limits, but not to its lowest possible value.

6. The rate of cooling from the high temperature—if not very rapid—has little influence on the magnitude of the effect.

7. The “sensitive state” does not wear off with time.

8. Mechanical vibration of the specimens considerably reduces the phenomenon.

9. The “sensitive state” is most pronounced in hard steels.

10. The effect is induced to a slight degree in some varieties of steel by temperatures as low as 100° C. It increases with increasing temperatures to about 700° C. Further increase in temperature has little influence.

11. Similar effects are noticeable in cast iron and in cobalt. The “sensitive state” is absent, or is present to only a very slight extent, in soft iron.

12. The effect has a maximum value for fields which give large values of μ, and tends to zero as the saturation point is approached.

Type
Proceedings
Information
Proceedings of the Royal Society of Edinburgh , Volume 28 , 1908 , pp. 239 - 248
Copyright
Copyright © Royal Society of Edinburgh 1908

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References

page 239 note * Phil. Trans. Roy. Soc., 1885, p. 570, §§ 54–58. Similar tests have been carried out by Searle, and Bedford, (Phil. Trans. Roy. Soc., 1902, p. 70)Google Scholar, but, with the exception of some quantitative determinations of the magnitude of the effect, little further information is given.