In situ ac magnetic susceptibility of gadolinium thin films

We report measurements of the ac magnetic susceptibility on Gd(0001)/W(110) thin films grown in ultrahigh vacuum. The measurements were made by using a pickup coil, in which the geometry and the number of turns were optimized. We applied an alternating magnetic field of about 2 Grms at frequencies of 180 and 340 Hz. The growth mode and the deposition rate of the Gd films were determined by performing conventional Auger electron spectroscopy during film growth. In films with thickness larger than 10 nm our technique is sensitive up to 1016 atoms/Grms, which allowed us to study the critical behavior of the magnetic susceptibility as the Curie temperature is approached from above, T→T%2bC. A sharp maximum, which may be related to the Hopkinson effect, is observed at a temperature T H ≊289 K.

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