Measurement of magnetic properties of thin films

A brief review of the theory necessary for an understanding of the magnetic properties is given. An astrometer is described which directly plots the critical curve of a sample on the calibrated screen of an oscilloscope. Fields HL (parallel to the hard axis) are created by two pairs of coils at right angles. The resultant field is scanned in time over a range exceeding the limits of the curve. The signals, picked up by an r.f. probe, are caused by the switching transients of the film and are used to modulate the intensity of the beam on the oscilloscope. The precision of measurement is of the order of 2%.