Abstract
An improved method is proposed for measuring dynamic magnetizations of bulk volcanic rock samples induced by a pulsed-field of 0.7 T and a duration of 10 ms. The transient magnetization is measured by a sensing system that consists of a pair of inductive differential coils, an analog preamplifier and integrator, and a high-speed digital storage scope. The system was calibrated using a paramagnetic salt (Gd2O3) and was tested to different kinds of volcanic rocks with their magnetic properties well-documented previously. The results were comparable with those measured by a quasi-static method using a vibrating sample magnetometer, although there were small discrepancies in hysteresis parameters suggesting the time-dependence of the magnetic properties. The proposed system provides not only the magnetization over the short interval of a pulse but also the rapid (~3 ms) exponential decay after a pulse. The decay time constant was different among the samples under study, indicating the variations of their magnetic relaxation time. Although the present system is not sensitive enough to characterize varieties of natural samples including sediments, it has the potential as a versatile and convenient tool for rock magnetism.
Highlights
Measurement of magnetizations during a short interval (1–10 ms) of a pulsed field generated by pulse magnet has long been employed in various fields of experimental physics (e.g., Grössinger 1982; Grössinger et al 1993; Miura 2007; Lv et al 2013)
The results suggested that it could be a promising tool for rock magnetism, but the sensitivity was still insufficient to be used as an alternative to the conventional, quasi-static method
The magnetization vs. time (M–t) curve and the field vs. time (H–t) curve, being scaled to their maximum peaks, have an equivalent shape (Fig. 2a). This led to the magnetization vs. field (M–H) plot in Fig. 2b, which is linear in the same manner as that obtained by the magnetic property measurement system (MPMS)
Summary
Measurement of magnetizations during a short interval (1–10 ms) of a pulsed field generated by pulse magnet has long been employed in various fields of experimental physics (e.g., Grössinger 1982; Grössinger et al 1993; Miura 2007; Lv et al 2013). The measurement of dynamic magnetizations in pulsed fields has been paid little attention except the pioneering work by Radhakrishnamurthy and Likhite (1987) who obtained hysteresis parameters from a set of synthetic and basalt samples using a laboratory-made PFM system (Likhite et al 1985). They compared the results both at room and low temperature (77 K), suggesting that the latter provided a better estimate of the composition and domain state. The results indicated the dynamic magnetization behaviors in a short duration of pulse (10 ms) as well as the rapid (3 ms) relaxation
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