A sensitive and versatile torque magnetometer for use in high magnetic fields

Abstract

We describe the design and construction of a sensitive dc torque magnetometer suitable for liquid as well as solid state samples. It can be used from room temperature down to very low temperatures (mK range) in magnetic fields produced either by superconducting or resistive magnets, in particular in the high fields (B≈30 T) produced by Bitter and hybrid magnets. The highest resolution that we have attained so far is about 0.3 pNm, which is mainly the result of a symmetric design. In typical laboratory conditions (at B=10 T) this corresponds to a magnetization resolution of about 3×10−11 emu. Other features include modularity, linearity, feedback and forward bias capabilities, and an in situ calibration of the signal.

Magnetometry of low-dimensional electron and hole systems

“…Wiegers et al [11] described a magnetometer whose design was optimized for low coupling to external sources of vibration. It consisted ( figure 1(c)) of a 17.6 mm diameter, hollow, lightweight cylindrical rotor with eight capacitance electrodes evenly spaced around its outer diameter, and the 3 by 5 mm sample mounted on a platform at its centre.…”

“…A plastic disc was mounted on the fibre with its face perpendicular to the fibre. On one side of the disc a semicircular capacitance electrode was evaporated, and electrically Schematic diagrams of the magnetometers of: (a) Eisenstein et al [6]; (b) Templeton [10]; (c) Wiegers et al [11]; (d) Matthews et al [12]; (e) Schaapman et al [13]; (f) Schwarz et al [14]. The magnetic field direction in (a) and (c) to (f) is vertical; in (b) it is horizontal.…”

Measurements of the magnetic properties of conduction electrons

“…These design features have reduced a parasitic link coupling with external vibrations. The resonant frequency of the suspended system is 1.5Hz, and the sensitivity threshold of this magnetometer can be estimated from the reported measurements of the oscillatory signal as δm ∼ 0.01µ B per electron, although slow variations of the background were a factor of 10 larger [12,13]. The authors estimated the threshold magnetometer sensitivity as 10 −13 J/Tesla, which is equivalent to δM = 10 10 Bohr magneton in field of 1 T.…”

Nonequilibrium magnetization of a two-dimensional electron gas in a static magnetic field

“…The magnetometer employed is modeled after a design by Wiegers et al 8 , with modifications for simultaneous transport measurement and is shown in the inset of figure 1.…”