A single domain grain model for the low-field constricted hysteresis loops of some basaltic rocks

Radhakrishnamurty, C.; Sastry, N. P.

doi:10.1007/bf03050410

Cited by 19 publications

(10 citation statements)

References 5 publications

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“…The principal assumptions regarding the interpretation of Rayleigh loops have been that broad and constricted loops are indicative of the presence of significant concentrations of interacting hyperfine grains which exhibit VSP properties, with increasing constriction corresponding to an increasing degree of grain interaction [Radhakrishnamurthy and Sastry, 1970;Neel, 1970]. Specimens dominated by stable single-domain grains do not exhibit loops.…”

Section: Quadrature Susceptibilitymentioning

confidence: 99%

Correlation between Rayleigh loops and frequency‐dependent and quadrature susceptibility: Application to magnetic granulometry of rocks

Bloemendal¹,

Barton²,

Radhakrishnamurthy³

1985

J. Geophys. Res.

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We report the results of measurements of frequency‐dependent and quadrature low‐field magnetic susceptibility of basalt specimens showing different types of low‐field hysteresis (Rayleigh) loop. A correlation among the three techniques is demonstrated, with specimens showing broad and constricted loops exhibiting relatively high‐frequency dependence of susceptibility and a high ratio of quadrature to in‐phase susceptibility. This result has implications for magnetic granulometry studies of rocks. Broad and constricted Rayleigh loops indicate the significant contribution of hyperfine grains to the magnetic properties of specimens; however, with the current instrumentation, low‐field hysteresis loop measurements are restricted to relatively strongly magnetic specimens. For weakly magnetic rocks and sediments, measurement of the frequency dependence of susceptibility or the quadrature susceptibility permits rapid identification of specimens in which hyperfine grains significantly influence the magnetic properties.

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Section: Quadrature Susceptibilitymentioning

confidence: 99%

Correlation between Rayleigh loops and frequency‐dependent and quadrature susceptibility: Application to magnetic granulometry of rocks

Bloemendal¹,

Barton²,

Radhakrishnamurthy³

1985

J. Geophys. Res.

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“…are too narrow to be observed with our equipment [Deutsch and Piitzold, 1976]. Radhakrishnamurty and Sastry [1970] point out that since the BHe/A values (5-20) for their samples that showed wide loops exceed the theoretical MD values by two or three orders of magnitude, the actual loops are unlikely to be due to MD grains, a conclusion supported by N•el [1970].…”

Section: Rayleigh Constants and He Is The Bulk Coercivity; Such Loopsmentioning

confidence: 69%

Inferences on the Magnetic Domain State of Leg 37 Basalts

Murthy¹,

Deutsch²,

Patzold³

1977

Initial Reports of the Deep Sea Drilling Project

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“…A further clue to the cause of large J, values in samples showing Rayleigh loops may be the fact that in 9 out of 17 samples from site 321 but in only one marginal case from hole 319A (sample 1-1,42-45) the loops were constricted (Figure 7). Radhakrishnamurty and Sastry [1970] and Ndel [1970] have attributed such constrictions to strong interaction in dense SP particle clusters. This should correspond to an intermediate case between SD and SP where one might expect both the remanence and the susceptibility to be large, as is indeed the case at site 321.…”

Section: Table 4) In Type I Samples the Most Striking Features Armentioning

confidence: 83%

Magnetism of basalt cores from the Nazca Plate and implications for magnetic anomaly interpretation

Deutsch¹,

Pätzold²

1976

J. Geophys. Res.

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Measurements of magnetic and thermomagnetic properties of basalt from leg 34 of the Deep‐Sea Drilling Project indicate that our 46 samples contained stable single‐domain (SD) or pseudo‐SD magnetite or titanomagnetite. The mean inclination after af and thermal demagnetization is Ī= −15°, close to the present dipole field, at site 321 but is anomalous (Ī = +53°) at site 319. In 31 samples of massive basalt from both sites the stable remanence at 20°C was masked by a low‐coercivity component. High‐field hysteresis loops are narrow at 20°C and broad below the −155°C magnetite transition. These samples, which we denote type 1, exhibited wide or constricted Rayleigh loops in 10 Oe. Although the magnetite in type 1 samples tends to be coarse (>100 μm), our findings demonstrate that the effective source of type 1 magnetite properties is not multidomain structures but fine predominantly superparamagnetic interacting particles that become stable SD at low temperatures. The other 15 samples (type 2), containing finer‐grained magnetite or titanomagnetite, were stable at 20°C, did not show Rayleigh loops, and produced highly irreversible thermomagnetic curves consistent with SD behavior and oxidation upon heating. Between 20° and 105°C all type 1 k‐T curves rose spectacularly towards a Hopkinson‐type peak, while the natural remanence and the Koenigsberger ratios (∼1–10 at 20°) decreased sharply. Therefore in areas underlain by such rocks, magnetic anomalies must be interpreted with care.

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A single domain grain model for the low-field constricted hysteresis loops of some basaltic rocks

Cited by 19 publications

References 5 publications

Correlation between Rayleigh loops and frequency‐dependent and quadrature susceptibility: Application to magnetic granulometry of rocks

Correlation between Rayleigh loops and frequency‐dependent and quadrature susceptibility: Application to magnetic granulometry of rocks

Inferences on the Magnetic Domain State of Leg 37 Basalts

Magnetism of basalt cores from the Nazca Plate and implications for magnetic anomaly interpretation

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