Weak magnetic materials

High-gradient magnetic separation Elective separation of weakly magnetic materials. Separation of inorganic-sulfur-containing particles from coal. 

These weak magnetic materials can also be characterised by the extent to which the magnetic field is able to penetrate into the sample, the magnetic permeability. The magnetic permeability of a compound, is defined by ... 

Figure 12.2 Weak magnetic materials differ in their response to an external magnetic field (a) no solid present (b) a diamagnetic solid repels the external field and the density of field lines in the solid decreases (c) a paramagnetic solid attracts the external field and the density of the magnetic field lines in the sample increases. B (induction) and H (magnetic field) decrease inside a diamagnetic solid and increase inside a paramagnetic solid...

The Gouy balance can readily be adapted for high-pressure measurements. In this case, the high-pressure sample tube ( bomb ) must be made of mechanically strong, but weakly magnetic material, e.g., berylco-25 alloy. The sample, normally in solution, is pressurized in the tube, locked, and put in the Gouy balance. 

One device is made up of samples of superconducting materials put inside a transformer a low-frequency small current in the primary creates a weak magnetic field. 

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