The Sign of Magnetization: Proposed Definitive Test for Paramagnetic Meissner Effect and Bulk Superconductivity

The sign of the magnetic response is a criterion for the classification of materials. It can also be a distinguishing property of a quantum state such as superconductivity. The experimental determination of magnetic susceptibility, or magnetization, is often complicated by the measurement protocol and by the geometry and nature of the sample. We propose an experimental procedure to definitively establish the sign of the magnetic suceptibility or magnetization. This test is based on the "superposition" or "sum and difference" technique. In this procedure a fiducial specimen is fabricated by attaching a piece of the unkown material to a (known) standard or marker. The net signal is a superposition of the contributions from the marker and the unknown. Diamagnetic Meissner effect is a hallmark of superconductivity. By our test this conventional behavior may be distinguished from the so-called paramagnetic Meissner effect. It can be a guide to the confirmatory tests in the future discoveries of new bulk superconductors.