24
3 Experiment
Fig. 3.3 (a) View of 1K Pot that is thermally connected to (b). SQUID chip and (c) sample holder
assembly holding the SQUID + sample assembly. The heater consists of a 100 Ohm
metal film resistor, again placed next to the SQUID+ sample assembly.
3.2 Spectrometer
The spin noise spectrometer (SNS) setup (Fig.3.4) consists of cylindrical sampleholder (SH), a ‘saddle’ that holds the SH and mounts it atop the SQUID chip, and the
SQUID circuitry. Commercially available QD 550 SQUID from Quantum Design
is used to construct the SNS. The SH has a concentric hole of diameter 1.4 mm
and length 5.7 mm to hold samples. The design of the SH is modular as samples
of varying geometries that can fit inside the concentric hole of the SH are easily
replaceable with the help of tweezers. Generally, rod-shaped samples of Dy 2 Ti 2 O 7
are studied in this experiment. A superconducting pickup coil consists of 6 turns of
thin NbTi wire of diameter ∼ 0.09 mm is closely wound around the outside of the
3 Experiment
Fig. 3.3 (a) View of 1K Pot that is thermally connected to (b). SQUID chip and (c) sample holder
assembly holding the SQUID + sample assembly. The heater consists of a 100 Ohm
metal film resistor, again placed next to the SQUID+ sample assembly.
3.2 Spectrometer
The spin noise spectrometer (SNS) setup (Fig.3.4) consists of cylindrical sampleholder (SH), a ‘saddle’ that holds the SH and mounts it atop the SQUID chip, and the
SQUID circuitry. Commercially available QD 550 SQUID from Quantum Design
is used to construct the SNS. The SH has a concentric hole of diameter 1.4 mm
and length 5.7 mm to hold samples. The design of the SH is modular as samples
of varying geometries that can fit inside the concentric hole of the SH are easily
replaceable with the help of tweezers. Generally, rod-shaped samples of Dy 2 Ti 2 O 7
are studied in this experiment. A superconducting pickup coil consists of 6 turns of
thin NbTi wire of diameter ∼ 0.09 mm is closely wound around the outside of the