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.