Pulsed-field magnetometry for rock magnetism

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 (Gd 2 O 3 ) 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.

Microwave-Assisted Solvothermal Synthesis of Nanocrystallite-Derived Magnetite Spheres

“…The advantage of this method is that it allows for the rapid acquisition of isothermal magnetization, and a higher magnetic field can be applied to the samples. This method is widely used for measuring the magnetization of strong magnets [ 53 ], ferromagnetic materials or superconductors [ 54 ] and ferromagnetic powder or volcanic rock [ 55 ]. Moreover, it was demonstrated by Kodama [ 56 ] that the measurement of the magnetization of nanoparticles using this method is acceptable and yields results similar to those yielded by the vibration method.…”

Special issue on “Recent advances in environmental magnetism and paleomagnetism”

“…A frontier letter by Kodama (2015) presented an improved method for measuring dynamic magnetizations of bulk volcanic rock samples induced by a pulsed field using inductive differential coils, a preamplifier, integrator, and a high-speed digital storage scope. The measured M-H curves are comparable to the branches of the corresponding hysteresis loops measured in a static field.…”