Vibrating coil magnetometer for milli-Kelvin temperatures

We report the development of a vibrating coil magnetometer (VCM) as combined with a top-loading dilution refrigerator for measurements of the magnetization down to millikelvin temperatures. The VCM offers unique measurement conditions, notably efficient cooling of the sample, data collection in uniform magnetic fields, the possibility to study strong magnetic anisotropies, fast data collection over a very wide range of magnetic fields, and the possibility of fast sample changes. In first measurements of the dipolar Ising magnet LiHoF₄ we readily achieved an excellent long-term stability of the vibration drive system of the VCM providing a sensitivity in excess of 10-4 emu.