System and method for non-destructive evaluation of surface characteristics of a magnetic material

A system for producing information characterizing the properties of a sample of magnetic material near the surface of the sample comprising, in combination:

• probe means magnetically coupled to the sample for (a) imposing a magnetic field on the sample and (b) detecting the magnetic response of the sample,
• energizing means driving the probe means for applying an alternating magnetic field at a plurality of frequencies selected to excite Barkhausen domains at different levels near but below the surface of the sample,
• detecting means coupled to the probe for detecting a complex magnetic Barkhausen response of the sample for more than one frequency selected to excite the Barkhausen domains, and
• processor means coupled to said energizing and detecting means for analyzing the characteristics of the respective detected complex Barkhausen responses at the applied frequencies to isolate at least frequency and amplitude information from each said response for determination of the surface characteristics of the magnetic sample excited by the alternating frequencies.