Measurement of the magnetic anisotropy of UPt3

Abstract

Using a capacitve torque-meter we have measured the magnetic anisotropy of UPt3 single crystals over a wide range of temperature and magnetic field. In high fields,X a,b shows the well-known maximum near 20K, but below 1T it shifts rapidly towards lowerT. FollowingX a,b −X c further down to 15mK, we observed a well defined border line where its temperature dependence suddenly stops. At intermediate fields this border line follows the upper critical field curve, separating from it both in higher and in lower fields.