Tunnel diode resonator for precision magnetic susceptibility measurements in a mK temperature range and large DC magnetic fields

Abstract

Precision radio-frequency measurements of the magnetic susceptibility using the tunnel diode resonator (TDR) technique are used to study the delicate effects in magnetic and superconducting materials. High resolution (in ppb range) measurements are particularly important for studies of the London and Campbell penetration depths in a superconductor and for the investigation of magnetic transitions in (anti)ferromagnets. Due to the small rf magnetic-excitation in a mOe range, the TDR is especially useful at low-temperatures in a mK range, if Joule heating generated in the TDR circuitry is efficiently removed and the circuit is stabilized with sub-mK precision. Unfortunately, the circuit has significant magnetic field dependence, and therefore, most of the precision TDR measurements at low-temperatures were conducted in zero magnetic field. In this work, we describe the design of a setup for precision TDR measurements in a dilution refrigerator down to ∼40 mK with a 14 T superconducting magnet. The key features of our design are the separated electronics components and the placement of the most field sensitive parts in the fieldcompensated zone far from the center of solenoid as well as the heat-sinking at a higher temperature stage. The performance of the working setup is demonstrated using several superconductors.

Campbell penetration depth in low carrier density superconductor YPtBi

“…The variation of the rf magnetic penetration depth λ m was measured in a dilution refrigerator by using a TDO technique [35] (for review, see Refs. [36,37]).…”

Campbell penetration depth in low carrier density superconductor YPtBi

“…The variation of the radio-frequency (rf) magnetic penetration depth ∆λ m was measured in a dilution refrigerator by using a tunnel diode oscillator (TDO) technique [35] (for review, see Ref. [36,37]).…”

Low-temperature high-frequency dynamic magnetic susceptibility of classical spin-ice Dy$_2$Ti$_2$O$_7$

“…Please see reviews [34,35,36] for the detailed description of the principles of the TDR technique used in the present work, and Ref. [37] for the technical discussion of the implementation of the TDR in a dilution refrigerator, which was used in our experiments in this work.…”

“…Essentially, the tunnel diode compensates for the losses and, when the impedances properly match, triggers spontaneous self-oscillations at f 0 . It is possible to maintain this state with minimal external noise and excellent stability, provided that the circuit itself is well stabilized and shielded [37,38]. The outstanding sensitivity of the technique comes from the fact that it operates in the frequency domain (similar to microwave cavity perturbation technique and NMR), but without the need to scan the frequency (or field) in search for the resonance, which is an added benefit.…”