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Radhakrishnamurty C Likhite S D Deutsch E R Murthy G S 《Journal of Earth System Science》1978,87(11):235-243
Journal of Earth System Science - Investigations involving temperature dependence of low-field susceptibility and of low- and high-field hysteresis have been carried out on more than one thousand... 相似文献
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C Radhakrishnamurty S D Likhite P W Sahasrabudhe 《Journal of Earth System Science》1978,87(11):245-254
A simple method for an in situ measurement of susceptibility and low-field hysteresis on rock bodies like dykes and flows is described. Extensive use of this method indicates that in some dykes and flows, the nature of the magnetic grains varies rapidly across the bodies. Making use of such observations, it seems possible to select stable rock samples for palaeomagnetic work and also understand to some extent the origin of remanent magnetization in different types of rock bodies. 相似文献
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C. Radhakrishnamurty S.D. Likhite P.W. Sahasrabudhe 《Physics of the Earth and Planetary Interiors》1977,13(4):289-300
The nature of magnetic grains in basalts obtained from different parts of the world has been investigated. Results indicate that magnetic behaviour attributable to cation-deficient magnetite is common in basalts younger than Cretaceous, while that due to multidomain magnetite is widespread in much older rocks. Superparamagnetic grains occur in basalts more abundantly than originally presumed, which seem to be mainly responsible for the viscous remanent magnetization of such samples. Basalts which are inferred to contain predominantly optimum single-domain grains are found to be most suitable for palaeomagnetic work. However, many samples generally contain a wide range of grain sizes and this can account for the observed variation in their magnetic stability. One possible mechanism for the formation of such magnetic grains in basalts and its implications to palaeomagnetism is presented. Basalts whose magnetic behaviour is completely reversible on heating and cooling are very rare and because of this fact the reliability of palaeointensity determinations, involving heating of the samples even for one time, may be reduced to a considerable extent. 相似文献
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C. Radhakrishnamurty S. D. Likhite E. R. Deutsch G. S. Murthy 《Physics of the Earth and Planetary Interiors》1982,30(4):281-290
The bulk magnetic properties, including Curie temperature, susceptibility and hysteresis at various temperatures, and the Mössbauer spectra of coarse synthetic members of the titanomagnetite series are compared as a function of titanium content, using some previously reported and some new results. It has been noted previously that the titanium-rich members fail to show the expected “true multidomain” behaviour observed in pure magnetite. One possible explanation is that the behaviour observed may be due to a tendency to inhibit domain wall formation in some titanomagnetites. In this paper we discuss some other possible mechanisms to account for the magnetic properties of such titanomagnetites observable even when domain-wall-related structures do form in them. These mechanisms suggest that magnetocrystalline anisotropy and its temperature dependence in titanomagnetites may be related to local magnetic inhomogeneities, and do not depend only on crystal structure as in the case of classical ferromagnetic materials. 相似文献
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A critical study on the type of the magnetic grains, both in composition and domain state, in rocks of different ages has
been carried out. One simple, fast and non-destructive test, which can provide useful information on the nature of the magnetic
grains in freshly collected samples, seems to be the ratio of susceptibilities at 77 and 300 K. This ratio, termed relative
susceptibility, ranges from 0·1, for samples containing 70% ulvospinel bearing titanomagnetite (TM70) to 1·50 for cation deficient
magnetite bearing ones. The results indicate that the value of 0·1 for TM70 is not greatly affected even if some amount of
TM80, which is nonmagnetic at 300 K, is present in a rock sample. However, the coercive force at 77 K will increase considerably
for such a sample. The effects of mixed compositions and domain states of magnetic grains on the overall behaviour of basalts
are discussed. 相似文献
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C. Radhakrishnamurty P. K. S. Raja S. D. Likhite P. W. Sahasrabudhe 《Pure and Applied Geophysics》1972,93(1):129-140
Summary Magnetic hysteresis studies at different fields and temperatures have been carried out on several basalts. From such studies it would be often possible to delineate the single or multidomain character of the sample and in some cases to identify the magnetic minerals in them. However, in determining the Curie temperatures of the basalts, especially of those containing predominantly single domain grains, several difficulties arise, which are discussed. 相似文献
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